The 10 Most Massive SPDR ETFs On The Market by InsiderMonkey.comAugust 31, 2013April 15, 202001076 No. 4 SPDR S&P MidCap 400 ETF (NYSEARCA:MDY) MDY data by YCharts Assets Under Management: $13.5 million The Index the ETF tracks: S&P MidCap 400 Index Average trading volume: $2.2 million Year-to-date return: 17.3% 1 2 3 4 5 6 7 8 9 10 11