Interest Rates in Mexico
The Role of Exchange Rate Expectations and International Creditworthiness

This paper explores how interest rates on domestic financial assets in Mexico are linked to expectations of exchange rate changes and to perceptions about the default risks contained in Mexico’s external debt. It is shown that the interest rate differentials between peso- and U.S. dollar-denominated domestic assets reflected some concerns about the exchange rate policy during the period under study. In addition, the evidence suggests that the interest rate on a U.S. dollar-denominated Mexican domestic asset is linked (i.e., cointegrated) to the yield implicit in the secondary market price for external debt issued by Mexico.

Abstract

This paper explores how interest rates on domestic financial assets in Mexico are linked to expectations of exchange rate changes and to perceptions about the default risks contained in Mexico’s external debt. It is shown that the interest rate differentials between peso- and U.S. dollar-denominated domestic assets reflected some concerns about the exchange rate policy during the period under study. In addition, the evidence suggests that the interest rate on a U.S. dollar-denominated Mexican domestic asset is linked (i.e., cointegrated) to the yield implicit in the secondary market price for external debt issued by Mexico.

I. Introduction

This paper investigates the recent behavior of interest rates in Mexico by exploring their links to expectations of exchange rate changes and perceptions about the default risk associated with holding Mexican financial assets. A central theme of the paper is the extent to which both the domestic and external U.S. dollar-denominated debt issued by Mexico are linked; namely, the extent to which the interest rate on domestic debt denominated in U.S. dollars and the implicit yield on external debt are closely associated on the basis of default risk. During the period covered in this study, namely from January 1987 to July 1990, 1/ the Mexican authorities were engaged in a major effort of macroeconomic adjustment and structural reforms including the liberalization of financial markets. In response, the inflation rate declined sharply from an average of 8 percent a month during 1987 to an average of 1 ½ percent per month since the middle of 1988. However, domestic nominal interest rates declined to a lesser extent and, in real terms, ex-post interest rates on domestic financial assets shifted from being negative during 1987 to being highly positive subsequently, notwithstanding an improvement in the overall fiscal performance on the basis of strong fiscal actions by the authorities.

It is in this context that we test the validity of the following hypothesis: the recent behavior of interest rates in Mexico has been closely linked to both expectations of exchange rate changes and to international perceptions of Mexico’s creditworthiness where the latter is assumed to be represented by the yield implicit in the secondary market price of external debt issued by Mexico. It is argued that this hypothesis will hold if there are no perceived differences in the credit standing of domestic and external debt of Mexico. This is so because in that case both the domestic and external debt would be subject to the same country risk premium.

The methodology adopted to give empirical content to this hypothesis is presented in Section II. As explained there, because of some important differences in the characteristics of domestic versus external debt issued by Mexico, the hypothesis is split in two components. The first part of the hypothesis concentrates on the role of expectations of exchange rate changes and states that some form of interest rate parity (covered and/or uncovered) should hold between two assets issued by the Mexican government which are identical in all respects except for the currency of denomination. The second part of the hypothesis deals with the country risk component of Mexican interest rates and states that the interest rate on domestic debt denominated in U.S. dollars should be closely linked to the yield to maturity implicit in the secondary market price issued by Mexico.

Section III tests the first component of the hypothesis. Our investigation shows that when applied to specific financial assets to be discussed below, deviations from the covered interest parity condition (CIP) have been small and random occurrences most of the time. However, significant but brief deviations from CIP have occurred in periods when uncertainties in the economy were unusually large, for instance between late 1987 and early 1988 when the authorities implemented a comprehensive adjustment program. The results from testing the uncovered interest parity hypothesis (UIP) suggest that the exchange rate policy suffered from a lack of complete credibility (also known as the “peso problem”) during the period under study. Under those circumstances, no strong conclusions can be derived about the validity of the UIP.

Section IV uses the observed price in the secondary market for Mexican external debt to obtain the implicit yield associated with holding assets issued by Mexico abroad. This section then uses cointegration techniques to show that domestic interest rates of Mexican assets denominated in U.S. dollars are closely linked to the behavior of the implicit yield derived from the secondary market for Mexican debt. This result, combined with our findings on interest rate parity, lead to an important policy implication, namely, that a sustained decline in domestic interest rates is linked not only to the elimination of the wedge between public expectations of exchange rate devaluations and the preannounced rate of depreciation but is also associated with an improvement in the underlying conditions on the Mexican economy which affect international perceptions about the creditworthiness characteristics of the country. Section V presents some preliminary conclusions.

II. Methodology of the Study

The main hypothesis of this study, advanced in the previous section, can be expressed as:

(1)(1+it)stEt(St+1)=(1+g(itsm))

where it is the domestic nominal interest at time t on peso-denominated treasury bills, itsm is the implicit yield at time t from the secondary market of Mexico’s external debt, St is the spot exchange rate at time t, defined as the price of one U.S. dollar expressed in Mexican pesos and Et(St+1) is the expected value at time t of the t+1 spot exchange rate conditional on information available in time t. Et(St+l)/St+l represents the expected rate of depreciation (or appreciation) of the Mexican peso.

Equation (1) states that domestic interest rates in Mexico, adjusted for expectations of exchange rate changes are linked (through a “g” function) to the implicit yield from the secondary market of Mexico’s external debt. That is, it is postulated that domestic interest rates in Mexico are closely associated to the international perception of Mexico’s creditworthiness, which is captured in the behavior of itsm. 2/ The implicit hypothesis behind this postulate is that there are no perceived differences in the credit standing of domestic and external debt of Mexico; so that both kinds of debt share the same country risk premium.

Equation (1) would have been a form of uncovered interest parity (UIP) between it and itsm if g were to take a unitary value. This is very unlikely, however, since the assets involved in equation (1) have very different maturities. Indeed, while the representative Mexican Treasury bills are of 28-days maturity, commercial bank claims on Mexico which are traded in the secondary market, have a long-term maturity that run between 20 and 30 years. Moreover, in contrast to the market for Mexican Treasury bills, the secondary market for Mexico’s external debt is subject to barriers to entry as each transaction requires high entry costs and complex documentation. In view of these differences, one cannot expect that domestic interest rates in Mexico, once taking expectations of exchange rate changes into account, would always equal the implicit yield on Mexico’s external debt. Instead, it is postulated that such variables “move together” at least in the long-run; that is, that they are cointegrated, where g is the parameter of cointegration.

To test this hypothesis, the following procedure was used. First, it was tested whether UIP held between two Mexican assets which have identical characteristics except for the currency of denomination. Then, it was tested whether a Mexican asset denominated in U.S. dollars was cointegrated with the implicit yield for Mexico’s external debt. The remaining of this section explains the rationale and the details of such procedures.

Since August 1986, the Mexican authorities have been issuing PAGAFES, 3/ an instrument denominated in U.S. dollars but payable in pesos at the prevailing controlled exchange rate. 4/ This asset is identical to the CETES, 5/ a peso-denominated treasury bill, except for the currency of denomination. Since both assets are issued by the Mexican government, they contain the same country-risk premium. The primary interest rates on both PAGAFES and CETES are determined during weekly auctions. Although the Bank of Mexico has intervened at times in order to tighten or ease monetary policy, by and large, interest rates have been freely determined. Furthermore, both assets are freely traded in the secondary markets although the market for PAGAFES is much thinner. Since the only difference between CETES and PAGAFES is the currency of denomination, if UIP holds, the interest rate differentials between the two assets should reflect only the expected depreciation (or appreciation) of the exchange rate in the controlled market.

That is, if UIP holds

(2)(1+it)=(1+it*)Et(St+1)St

where, from now on, it will refer specifically to the 30-day nominal yield on 28-day nonindexed domestic treasury bill (CETES) at time t and it* is the 30-day nominal yield on 28-day domestic treasury bill (PAGAFES) at time t. 6/

Equation (2) is tested in Section III. The test enables one to determine the role of expectations of exchange rate changes on the behavior of the interest rates on CETES. Notice also that the hypothesis contained in equation (1) can be framed in terms of covered interest parity (CIP). That is, a CIP version of equation (1) is:

(3)(1+it)StFt=(1+g(itsm))

where Ft is the 30-day forward exchange rate at time t.

Correspondingly, a CIP version of equation (2) is:

(4)(1+it)=(1+it*)FtSt

Section III will explore the validity of both the covered and uncovered versions of interest rate parity, namely it will test whether equations (2) and (4) held in Mexico during the period under study.

Next, we have to deal with the country risk component of domestic interest rate. Notice that equations (1) and (2) (or equations (3) and (4)) imply:

(5)it*=g(itsm)

Therefore, equation (5) states that the interest rate on PAGAFES is some function of the yield to maturity of Mexico’s external debt. This equation holds true for either the covered or uncovered version of interest parity.

As mentioned before, the maturities (and some other market characteristics) of Mexico’s external debt and PAGAFES are very different. However, if the main hypothesis of this paper is true (namely, that after taking expectations of exchange rate changes into account, domestic interest rates are linked to the implicit yield on Mexico’s external debt), one would expect the two interest rates to “move together” at least in the long-run; that is, we postulate that it* and itsm are cointegrated. Section IV presents tests for that hypothesis.

III. Covered and Uncovered Interest Rate Parity

CIP and UIP are alternative hypotheses about the nominal interest rate differentials between financial assets that are identical in all respects except for the currency of denomination. CIP relates this interest rate differential to the forward premium (or discount) on foreign exchange, while UIP relates the interest rate differential to the expected change in the spot exchange rate between the currencies of the two countries over the holding period. 7/

1. Covered interest parity (CIP)

Equation (4) represents a CIP relationship between CETES and PAGAFES. Chart 1 presents the evolution of (1+it) and (1+it*) (Ft/St) over the period January 1987 to July 1990. The chart shows that deviations from covered interest arbitrage were small for most of the observations with notable exceptions occurring between November 1987 and March 1988. That period, however, coincided with the beginning of the current stabilization program in Mexico, when a series of structural reforms were announced, a major devaluation took place and the authorities implemented a price-wage pact between the government, labor and business with the aim of controlling prices. These developments undoubtedly increased uncertainties about the future course of the economy which, combined with some official intervention in domestic financial markets, might have prevented covered arbitrage from holding.

Chart 1
Chart 1

Mexico: Cetes Vs Pagafes (Adjusted) 1/

Citation: IMF Working Papers 1991, 012; 10.5089/9781451925388.001.A001

nb. The unit on the y-axis is 1 + I, where I is the interest rate per month.1 Adjusted for the Dremium in the forward market.

An analysis of the deviations from CIP is presented in Table 1. As the table shows, 71 percent of the deviations are less than 0.5 percentage point and 86 percent of the deviations are less than 1 percentage point. By comparison, the average bid-ask spreads of the exchange rate in the controlled and the free markets during the period were 0.95 percent and 2.1 percent, respectively. Besides being small, the deviations from interest parity have a mean very close to zero and are uncorrelated at all lags. Indeed, the results of a Q test for serial correlation indicate that the null hypothesis that the series is white noise cannot be rejected at the 1 percent significance level.

Table 1.

Analysis of the Deviations from Interest Rate Parity

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The null hypothesis of no serial correlation is rejected at the 1 percent level only if the value of χ2 is greater than the critical value of 21.7.

The above results indicate that, with the exception of a short period of time, when uncertainties in the economy were unusually large, deviations from interest rate parity have been small and random occurrences. This evidence seems to provide strong support for CIP. 8/

2. Uncovered interest parity (UIP)

The uncovered version of interest parity between CETES and PAGAFES is represented by equation (2).

The empirical literature on UIP has broadly tested equation (2) (see, for example, Cumby and Obstfeld (1980) and Lizondo (1983a)). However, since Et(St+1) is an unobservable variable, the empirical tests have been joint tests of equation (2) and two hypotheses of expectations behavior: (1) the rational expectations hypothesis that states that Et(St+1) is a mathematical conditional expectation, based on the true probability distribution underlying the behavior of the exchange rate; and (2) the hypothesis that the foreign exchange market is “weakly” efficient in that expectations of the future exchange rate incorporate all information contained in past forecast errors of the exchange rate. These joint hypotheses imply that the forecast error:

(6)ϵt=St(1+it)(1+it*)St+1

should have zero mean and be serially uncorrelated.

The joint hypothesis containing UIP and the hypothesis of “weak” market efficiency was tested for Mexico using non-overlapping monthly observations covering the period January 1987-July 1990. Before discussing the results of the tests, it should be pointed out that over this period, the exchange rate was not freely floating but managed by the authorities and followed three different regimes: (1) from January 1987 to December 1987 the exchange rate was depreciated by an unspecified amount each day; (2) from January 1988 to December 1988 the exchange rate was fixed except for a small change in February; and (3) from January 1989 to May 1990 the exchange rate was depreciated by an announced 1 peso per U.S. dollar a day. 9/ Recent studies have analyzed the problems involved in testing the UIP hypothesis in the presence of intervention in exchange rate markets. In particular, Krasker (1980) and Lizondo (1983b) have shown that in the presence of a small and positive probability of a devaluation, an efficient exchange rate market will imply that the expected value of the future spot rate will reflect the probability of that event. However, as long as the devaluation does not take place, the expectation of the future spot rate will consistently overestimate the realized future spot rate. As a result, the forecast error in the exchange market will show a positive bias, 10/ but this will not be sufficient to reject the joint hypothesis that UIP holds and that the market is “weakly” efficient.

Table 2 presents an analysis of the forecast error ϵt. The most important result is that although the Q test indicates that at the 1 percent significance level we cannot reject the hypothesis that the errors are uncorrelated, the mean of the forecast error is positive. 11/ These results imply that St((1+it)/(1+it*)) overstates the future spot rate. Based on our previous discussion, however, the existence of a positive mean in the forecast errors does not allow us to accept or reject that UIP holds under conditions of “weakly” market efficiency, since the tests for UIP are not appropriate in the context of a “peso problem.” However, the lack of autocorrelation in the forecast errors seems to indicate that the interest rate differentials between CETES and PAGAFES incorporated all the information available to generate predictions of the future exchange rate in conditions where the “peso problem” prevailed, namely in a situation where the exchange rate was not allowed to float freely and there was always a small probability of a devaluation. 12/ Indeed, the differential between the spread in the interest rates on CETES and PAGAFES and the preannounced depreciation of the exchange rate was greatest in the early part of 1988 following the transition to a fixed exchange rate regime, which can be taken as an indication of a lack of full credibility in the exchange rate policy (Chart 2). However, as the authorities persisted in their policies and financial conditions improved, the differential has tended to decline.

Table 2.

Analysis of the Forecast Error

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The critical value for the test with nine degrees of freedom at the 1 percent level is 21.7.

Chart 2
Chart 2

Mexico: Interest Rate Differentials. Vs Exchange Rate Depreciation

Citation: IMF Working Papers 1991, 012; 10.5089/9781451925388.001.A001

IV. Domestic Interest Rates and the Risk of Default in the Secondary Market for Mexico’s External Debt

In the previous section we showed that the interest rate differentials between domestic nonindexed assets (CETES) and dollar-denominated domestic assets (PAGAFES) have, in general, satisfied the CIP condition. The evidence also seemed to indicate the presence of a “peso problem,” and, therefore, the interest rate differentials may be attributable to expectations of large exchange rate changes (which actually did not take place). These results, however, do not explain the persistence of high interest rates on domestic dollar-denominated assets (PAGAFES); these ranged between 14 percent and 44 percent per annum in the period under study. In the context of a relatively open economy with few restrictions on financial flows, a plausible explanation is that all Mexican assets (indexed or not) contain a risk premium that reflects the market perception of the country’s credit standing. Therefore, it can be argued that the interest rate differential between PAGAFES and a risk-free asset reflects primarily the country-risk premium. 13/ Chart 3 shows the recent evolution of the interest rate on PAGAFES versus LIBOR, which can be considered a relatively risk-free interest rate.

Chart 3
Chart 3

Mexico: Interest Rates On Pagafes Vs Libor

Citation: IMF Working Papers 1991, 012; 10.5089/9781451925388.001.A001

In this section, the hypothesis, as represented in equation (5), that the interest rate on PAGAFES is linked to the yield to maturity implicit in the secondary market price for external debt issued by Mexico is tested. The rationale behind this hypothesis is that, from the point of view of creditworthiness, there should be no distinction between the domestic and external components of the debt. 14/ Hence, the country risk premium implicit in the secondary market price for Mexican debt issued abroad should be equal to the country-risk premium contained in domestic debt of identical characteristics.

As mentioned in Section II, in testing the above hypothesis, one encounters the problem that the characteristics of the assets, i.e., external claims on Mexico and PAGAFES, are very different in terms of maturities and market access. 15/ However, if our hypothesis is correct, one would expect the two interest rates to “move together”, at least in the long-run.

Traditional econometric theory cannot help in testing the hypothesis A basic assumption underlying most econometric analyses is that the data processes involved are stationary and ergodic. As will be shown below, however, the series for both PAGAFES and the implicit yield for Mexico’s external debt are integrated processes of order one, I(1), and become stationary only in their first difference. Since the original series are nonstationary, the means and variances of the series are not constants, and the usual statistical properties of convergence to the population mean and variance do not apply. As a result, traditional regression analysis relating the behavior of these variables might just reflect “spurious correlations.” Recent developments in cointegration analysis, however, has provided a tool to analyze if there is a meaningful close relationship in the long-run for variables that are 1(1) processes. 16/

Two variables, x and y, following an I(1) process are said to be cointegrated if there exist a constant A, such that

(7)zt=xtAyt

is a stationary process; that is the series zt is integrated of order zero, I(0). An important result of cointegration analysis is that if two variables are I(1) and cointegrated, there must be Granger causality in at least one direction, as one variable can help forecast the other. 17/ This corollary will be used in interpreting the results.

The rest of this section will proceed as follows: first, we will derive the yield to maturity implicit in the secondary market price of Mexico’s external debt; then we will test the hypothesis that the interest rate on PAGAFES can be explained by the yield to maturity in the secondary market by testing if both variables are cointegrated, and the direction of the Granger causality. Finally, we present an “error correction” model of the short-run dynamics of the adjustment process.

1. The implicit yield in the secondary market for Mexico’s external debt

The implicit yield to maturity for Mexico’s external debt was obtained from the observed secondary market price on Mexico’s external debt (Pt) (from Solomon Brothers data) 18/ and the application of the following present value formula:

(8)Pt=Σk=1nCt(1+itsm)k+FV(1+itsm)n

where itsm represents the implicit annual yield to maturity evident in the secondary market price for Mexico’s external debt in period t. The face value (FV) is set at 100 since the discounts quoted in the secondary markets apply to US$100 worth of contractual debt; the contractual coupon payment (Ct) is the interest rate on six month LIBOR plus the interest rate spread paid by Mexico (assumed to be 13/16 percent over the entire period); and the average maturity (n) was assumed to be equal to 20 years. A monthly series itsm for was constructed covering the period August 1986-July 1990.

In modeling the market value of claims of debtor countries, Dooley (1988) has argued that the secondary market price of debt should equal the creditor’s expected present value of total debt service payments. This argument, which requires the assumption that creditors are risk-neutral can be formalized as:

(9)Pt=Et[Σk=1nCt(1+itf)k+FV(1+itf)n]

where Et is the expectations operator during period t and itf stands for the risk-free market rate (which in this case is taken as corresponding to the rate on six-month LIBOR prevailing at period t).

A comparison between equations (8) and (9) reveals that the implicit yield obtained from the price in the secondary market depends on the creditor’s expectations about receiving full payments on the contractual debt. The derivation of a specific formula for the probability of default on Mexico’s external debt is subject to specific assumptions about the distributional properties of debt service payments. 19/ In what follows, no attempt is made to derive a measure of the probability of default. Instead, by testing the hypothesis that the long-run behavior of the interest rate on PAGAFES can be explained by the behavior of the implicit yield for Mexico’s external debt, one is also implicitly testing the hypothesis that the probability of default on Mexico’s external debt also applies to Mexico’s domestic debt. 20/.

2. The test for cointegration

The first step is to test whether the series on interest rate on PAGAFES (it*) and on the implicit yield from the secondary market (itsm) are I(0), i.e., to test whether the series are stationary. This is done by using the Dickey-Fuller (DF) test and the Augmented Dickey-Fuller (ADF) tests. In both tests, the null hypotheses are that the series have unit root and the alternative hypotheses are that the series are I(0). The ADF test consists in running the following regressions using OLS:

(10)Δit*=β1it1*+Σj=1Pγ1,jΔitj*+ω1,t
(11)Δitsm=β2it1sm+Σj=1qγ2,jΔitjsm+ω2,t

where the number of lags in each equation (p or q) is selected such as t and ω1, t and ω2, t are white noise. The difference between the DF test and the ADF test is that in the former γ1, j = γ2, j = 0.

In both the DF and the ADF tests, the test statistic is the ratio of each βi (i=1,2) to its corresponding standard error. The null hypothesis is rejected if the βi is negative and significantly different from zero. 21/

The results from the tests are presented in Table 3. The tests covered the period August 1986-July 1990. In the case of the ADF test, two lags were needed for t to be white noise (that is, p=l in equation (10)), while only one lag was enough for ç to be white noise (that is, q=2 in equation (11)). As shown in the table, the null hypothesis of unit root cannot be rejected at the 5 percent significance level indicating that the series on both interest rates on PAGAFES and the implicit yield for Mexico debt are nonstationary processes (Chart 4).

Table 3.

Unit Root Test for it* and itsm

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The number in parenthesis indicates the number of lags sufficient for ωi, t (i=l,2) to be white noise.

Chart 4
Chart 4

Mexico: Interest Rate On Pagafes Vs Yield To Maturity

Citation: IMF Working Papers 1991, 012; 10.5089/9781451925388.001.A001

Since the test statistics for it* are negative, it can be concluded that it* follows an I(1) process. However, since the test statistics for itsm are positive, it is necessary to test for the stationarity of the first difference, that is Δitsm. Indeed, the test statistics for Δitsm are negative and significant, implying that the original series is I(1). The result that it* and itsm are I(1) is in line with the hypothesis of rational expectations and market efficiency.

As discussed above, given the characteristics of PAGAFES and commercial bank claims on Mexico traded in the secondary market, it is reasonable to expect divergence in the behavior of the variables in the short-run; however, we would expect the variables to move together in the long-run. To test if the two variables are cointegrated, we need to first form the cointegration equation:

(12)i^t*=Ai^tsm+zt

where, as mentioned before, zt should be an I(0) process if it* and itsm are cointegrated. In this sense, zt measures the extent to which the system deviates from the long-run relationship between it* and itsm. If zt is stationary, such relationship will hold in the long-run.

An estimate of A, the long-run coefficient relating it* and itsm, is derived from the following vector autoregression (VAR) model:

(13)it*=1.089(8.050)it1*0.325(2.353)it2*+1.184(3.509)it3sm0.978(2.841)it5smR2=0.693

where the numbers in parenthesis are t-values.

Using (13) to obtain the long-run relationship between it* and itsm, the estimated form of equation (11) is:

(14)i^t*=0.872itsm

where i^t* is the estimated value of it* and zt=it*i^t*

To test whether zt is an I(0) process, i.e., to test whether it* and itsm are cointegrated, we used again the DF and ADF tests. In addition we also analyzed the Durbin-Watson of the cointegration equation (CRDW). In the context of the present exercise, this test consists in obtaining the Durbin-Watson statistic from running zt against a constant. The null hypothesis that zt has a unit root will be rejected if the CRDW is significantly above zero.

The results from the tests are presented in Table 4, and they are somewhat mixed. The CRDW test rejects the hypothesis of a unit root in the residuals of the cointegration equation at the 5 percent significance level and therefore supports the hypothesis that it* and itsm are cointegrated. However, both the DF and ADF tests do not support the hypothesis of cointegration at the 5 percent significance level. The DF statistics is significant at the 10 percent level but the ADF statistics is on the borderline.

Table 4.

Tests for Cointegration Between it* and itsm

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The literature reports values ranging from -2.89 (Schwert (1988) to -3.17 (Hall and Henry (1989)).

Hall and Henry (1989) report a value of -2.84; which likely corresponds to the upper end of the range.

Since our results are not conclusive, we further investigate whether it* and itsm are cointegrated by exploring if there exist a generating mechanism having what is called an “error-correcting” form: 22/

(15)Δit*=-ρ1zt1+lagged(Δit*,Δitsm)+d(B)vt

where dB is a finite polynomial in the lag operator B and vt is white noise.

Equation (14) is, therefore, a standard Error Correction Model (ECM) which includes the lagged residuals of the cointegration regression. The variables it* and itsm will be cointegrated if ρ1, the coefficient of the lagged error term, is significantly negative. This is so because equation (15) indicates that the amount and direction of a change in it* will take into account the size and sign of the previous deviation from equilibrium zt-1. If the variables are cointegrated, zt is stationary and, therefore, it is inclined to move towards its mean (which is zero), and hence the equilibrium relationship (14) tends to be restored.

Table 5 presents the results from estimating a simple ECM that includes the lagged error term zt-1 Since ρ1 is significant at the 5 percent level, this implies that there exists an error correlation mechanism that tends to restore the long-run equilibrium relationship between it* and itsm. Therefore, this test supports the hypothesis that it* and itsm are cointegrated.

Table 5.

Error Correction Model 1/

(Dependent variable: Δit*)

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It includes only the lagged variables that were found to be significant.

Finally, as mentioned above, an important result of cointegration analysis is that if two variables are I(1) and cointegrated, there must be Granger causality in at least one direction. Our prior is that, Mexico being a small open economy, the implicit yield for Mexico’s external debt Granger-causes the domestic interest rates on PAGAFES. Since the Granger test is an F test, it is applicable only to stationary variables; therefore, the test is applied to the first differences of it* and itsm. Table 6 reports the results from this test. As is shown, when Δit* is the dependent variable, the F value is significant at the 5 percent level, supporting the hypothesis that itsm Granger-causes it*. Moreover, the test rejects the hypothesis that it* Granger-causes itsm since the F value was found to be not significant at the 5 percent level when Δitsm treated as the dependent variable.

Table 6.

Tests for Granger Causality

(Dependent variable: Δit*)

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significant at the 5 percent level.

On balance, the evidence seems to support the hypothesis that it* and itsm are cointegrated. Nevertheless, the tests are not very robust and further investigation would be useful as more data become available.

V. Concluding Remarks

This paper explored whether domestic interest rates in Mexico can be linked to expectations of exchange rate changes and to perceptions of the default risk contained in Mexico’s external debt.

Tests were conducted on the covered interest parity (CIP) and uncovered interest parity (UIP) hypotheses using two assets that contain the same country risk premium but differ in the currency of denomination. It was shown that, with the exception of a short period of time when uncertainties in the economy were unusually large, deviations from covered interest parity were small and random occurrences. In addition, the evidence suggests that the “peso problem” prevailed during the period under study; that is, expectations of the future spot exchange rate consistently overestimated the actual future rate, in a regime where the exchange rate was not allowed to float freely. This result is consistent with rational expectations and efficiency in the exchange rate market and does not allow one to reject the validity of the UIP hypothesis.

A central issue in the paper was to investigate the extent to which both the domestic and external U.S. dollar-denominated debt issued by Mexico behave in the same fashion, i.e., that they are affected by the same considerations about prospects of the Mexican economy as reflected in the risk of default. In this context, this paper raised the hypothesis that the interest rate on a U.S. dollar-denominated domestic asset is linked to the yield implicit in the secondary market price for external debt issued by Mexico. This implies that, from the point of view of creditworthiness, there is no distinction between the domestic and external components of Mexican debt. The empirical tests conducted in this paper provide support for this hypothesis. It was found that, on balance, the evidence suggests that, once covered for exchange rate changes, domestic interest rates in Mexico and the implicit yield derived from the secondary market for Mexican external debt are cointegrated, i.e., they move together in the long-run. Moreover, it was shown that while the latter variable Granger causes the former, the inverse relationship does not hold.

An important policy implication derived from these results is that in order to achieve a permanent decline in domestic interest rates, the policies undertaken by the Mexican authorities need to be successful not only in reducing the wedge between public expectations of exchange rate devaluations and the preannounced rate of depreciation, but also in improving the underlying conditions of the economy which affect international perceptions about the creditworthiness characteristics of the country. This paper has not attempted to explain the factors underlying such perceptions of creditworthiness in Mexico. Such a task remains as a crucial next step in the current research.

Interest Rates in Mexico: The Role of Exchange Rate Expectations and International Creditworthiness
Author: Hoe Ee Khor and Ms. Liliana Rojas-Suárez