World’s biggest ETF sees record $21 billion flow on stock rally

SPY’s inflows coincided with several events known to increase trading activity, said Matt Bartolini, head of SPDR Americas Research at State Street Global Advisors. Friday was the final trading day before the S&P 500 and Nasdaq 100’s rebalancings went into effect, which can prompt funds managing trillions of dollars to readjust to align with new index compositions.