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Tara Iyer 0000000404811396 https://isni.org/isni/0000000404811396 International Monetary Fund

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References

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Appendix

I. Crypto-Equity Spillover Model

The Diebold-Yilmaz (2012 and 2014) interconnectedness and spillover model used in the empirical analysis is outlined below, with further details available in the original papers.

Consider an N variable covariance-stationary data-generating process xt = Θ(L)ut, where Θ(L) = Θ0 + Θ1L + Θ2L2 + ... and E[utut]=I, which is estimated using a vector autoregression (VAR) model. Taking the variance decomposition of this process yields the following forecast error variance decomposition (FEVD) matrix, with each element dij indicating the spillover from the jth variable to the i ith variable:

article image

The diagonal elements in the matrix (dii) contain the spillovers to self, while the off-diagonal elements capture the spillovers from other variables. For the purpose of the analysis here, only the cross-variance decompositions are counted, and self-spillovers are excluded. The last column of the table above provides the total spillovers to variable i from all other variables in the model, while the last row contains the total spillovers from variable j to all other variables in the system. Thus, the total spillover to each variable i in the VAR is derived as the sum of the off-diagonal elements in the row for that particular variable i, so that the total directional connectedness from others to CiH, is

CiH=Σj=1NdijHji(1)

Similarly, total spillovers to other variables in the system from each variable j, or CjH, is the column sum associated with j, excluding self-spillovers, that is,

CjH=Σi=1NdijHij(2)

Net spillovers are defined as the difference between (1) and (2). Total interconnectedness, CH, among the variables in the system is defined as the sum of all the off-diagonal entries of the FEVD, so that

CH=1NΣi,j=1NdijHij(3)

Diebold and Yilmaz use the generalized forecast error variance decomposition (GVD) method derived in Pesaran and Shin (1998) to identify the VAR. GVDs have the advantage of being order-invariant unlike Cholesky ordering schemes, which can potentially be arbitrary.20 GVDs allow for correlated shocks, implying that the H-step ahead variance decomposition matrix DgH=[dijgH] has entries

dijgH=σjj1Σh=0H1(eiΘhΣej)2Σh=0H1eiΘhΣΘhei(4)

As inputs to the VAR model to estimate the sequence of FEVDs, we use two transformations of the relevant variables: returns and volatility. Returns are defined as the percentage daily change in the closing price of crypto assets and equity indices, excluding trading holidays, while volatility is computed as the standard deviation of absolute percentage changes in intra-day prices (see Table A1). The VAR is estimated over a rolling window of 100 days over two different sample periods: Jan 2017-Dec 2019 and Jan 2020-Nov 2021.

II. Data

The variables used in the VAR analysis and the data sources are described in Table A1. All variables are in daily frequency, unless otherwise noted.

Table A1.

Variable Description and Data Sources

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III. Additional Results

Table A2.

Crypto-Equity Volatility Spillovers in Emerging Markets

article image
Sources: CryptoCompare; Yahoo Finance; author’s calculations. Notes: The spillovers are based on model estimation using daily volatility data for the time periods January 2017–December 2019 and January 2020– November 2021. In tables a and b, for the i-th row and j-th column in the matrix, the ij-th entry represents the spillover from asset j to asset i or the percent of forecast error variance of asset i due to shocks from asset j Rows add up to 100 percent. EM = emerging market.
Table A3.

Crypto-Equity Return Spillovers in Emerging Markets

article image
Sources: CryptoCompare; Yahoo Finance; author’s calculations. Notes: The spillovers are based on model estimation using daily returns data for the time periods January 2017–December 2019 and January 2020– November 2021. In tables a and b, for the i-th row and j-th column in the matrix, the ij-th entry represents the spillover from asset j to asset i or the percent of forecast error variance of asset i due to shocks from asset j Rows add up to 100 percent. EM = emerging market.
1

The author would like to thank Tobias Adrian, Fabio Natalucci, Mahvash Qureshi, Jerome Vandenbussche, Evan Papageorgiou, and Tomohiro Tsuruga for many helpful suggestions, and reviewers at the IMF Monetary and Capital Markets Department, Research Department, Strategy, Policy, and Review Department, and Communications Department for useful comments.

2

Adrian and Weeks-Brown (2021) discuss the risks associated with adopting crypto assets as a national currency, and Adrian, He, and Narain (2021) write about the risks associated with an unregulated crypto ecosystem. For a detailed discussion of the trends of crypto adoption (“cryptoization”) in emerging market economies and the risks and opportunities, see IMF (2021).

3

In November 2021, Bitcoin and Ether accounted for about 40 and 20 percentof total crypto market cap, respectively, while Tether, the largest stablecoin and in the top five crypto assets by market cap, accounted for about three percent of total crypto market cap.

4

The increase in crypto asset market capitalization is quite stark even when compared to the total US stock market capitalization, which itself has increased significantly since the pandemic. In early 2019, crypto asset market cap was about 0.4 percent of total US stock market capitalization, but this has increased to close to 5 percent in September 2021.

5

Several studies report limited interconnectedness between crypto and conventional assets such as equities and currencies in the pre-pandemic period (for example, Briere and others 2015; Dyhrberg 2016; Shahzad and others 2019; Guesmi and others 2019; Charfeddine and others 2020; Symitsi and others 2018; and Umar and others 2021), but note that spillovers increase during market stress episodes and may have been rising (Zeng and others 2020; Conlon and McGee 2020; and Maniff and others 2020).

6

Interconnectedness in this note is measured in terms of correlations, which provide a sense of the strength of the overall association between two variables, as well as spillovers, which indicate the impact of one variable on the other.

7

There might, however, be other potential risks associated with Tether, including a high observed failure rate of stablecoins, and the fact that Tether may not be fully backed by reserves at all times (Mizrach 2021 and Griffin and Shams 2020).

8

The S&P 500 index is considered among the best gauges of large-cap equity market movements in the United States, while the Nasdaq is a tech-heavy market-cap-weighted index of more than 2500 stocks, including some of the largest companies in the United States. The Russell 2000 index is a weighted index of 2000 small-cap companies in the United States and is a measure of the investment opportunities afforded by small cap stocks.

9

While stablecoins are usually pegged to the US dollar and other fiat currencies, small deviations from the market reference are common and rapidly reversed through arbitrage, generating the observed variations in prices.

10

Looking at the various sub-components of the S&P 500 index (such as consumer discretionary and staples, industry, healthcare, technology, and financials), the return (volatility) correlation of Bitcoin and Tether have increased significantly for all sectors and range between 0.27 to 0.38 (0.28 to 0.65) and –0.06 to –0.15 (0.19 to 0.35), respectively.

11

The MSCI index is a widely quoted equity market index that tracks the performance of mid- and large-cap equities across 27 emerging market economies.

12

The underlying premise of the approach is that the variance decomposition matrix associated with an N variable data generating process forms a weighted and directed network that can be used to estimate the direction and magnitude of spillovers among the variables, based on the share of the forecast error variation attributable to other variables. See appendix for further details.

13

The baseline model includes Bitcoin and Tether which have had the highest trading volumes for most of the pandemic (October 2021 Global Financial Stability Report, Chapter 2). Including Ether in the model does not significantly alter the results for the other assets in the VAR system, while its volatility and returns spillovers are estimated to be generally quite small. The Nasdaq index is also excluded from the model given its high correlation with the S&P 500 index, but the results are qualitatively robust to including it instead.

14

Considering the T-bill rate in first differences rather than in levels does not affect the results. Moreover, while the VIX is excluded from the baseline specification for the volatility VAR model as it tracks S&P volatility closely, the results remain qualitatively robust when including it as an additional exogenous variable. The VIX is included in the VAR model for returns.

15

Returns are defined as one-day log differences, whereas volatility is based on intra-day spreads with volatility = 0.361*[Ln (High Price) – Ln(Low Price)^2] following the formula used in Diebold-Yilmaz (2012). See the appendix for further details.

16

As in Diebold-Yilmaz (2012), the length of the forecast horizon and rolling window is considered to be 10 days and 100 days, respectively, but the results are robust when considering longer durations (20 days and 150 days, respectively).

17

While Bitcoin and Tether price movements are also highly correlated (the correlation is about 0.5 for price volatility and –0.25 for returns in 2020–21), the spillovers for Tether to equity prices are obtained controlling for Bitcoin prices in the VAR.

18

This note considers emerging market economies as countries that are included in the MSCI emerging market index.

19

The baseline specification of the VAR was checked against various alternative specifications for robustness, including using the VIX as an exogenous variable and replacing the S&P 500 index with the Nasdaq index. The core set of findings remain qualitatively similar.

20

Pesaran, H., and Y. Shin. 1998. “Generalized Impulse Response Analysis in Linear Multivariate Models.” Economic Letters 58, 17–29.

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Cryptic Connections: Spillovers between Crypto and Equity Markets
Author:
Tara Iyer