The sources of external imbalances in the run-up to the financial crisis vary widely across the seven systemic economies studied here, largely reflecting factors that have led domestic saving behavior to differ significantly. The case studies indicate that global imbalances have been driven primarily by saving imbalances—generally too low in advanced deficit economies and too high in emerging surplus economies—owing to a combination of equilibrium factors (demographic patterns), structural weaknesses, and domestic distortions. This implies that corrective steps at the national level as discussed in each country chapter—as part of collaborative action to address structural impediments and underlying distortions—will be needed to better support G20 growth objectives.