Before 2011:Q4, second quarter level is benchmarked to data on rest of the world holdings of money market mutual funds from internal FR Board, IF Division, Survey of Foreign Portfolio Investment in the United States. Quarters between benchmarks are linearly interpolated. Beginning in 2011:Q4, levels are estimated as a share of TIC form SLT, Fund shares, Grand Total. The ratio of money market mutual funds to total funds is calculated from the Survey of Foreign Portfolio Investment in the United States. Unadjusted flow is the change in the level; data for the most recent ten years show no significant seasonality.