ETF assets grew $20.8 billion or 3% in August according to State Street Global Advisors. ETF assets now total $661 billion across 755 ETFs.

Market Cap ETFs saw the biggest growth in August, increasing $9.6 billion or 6.0%. Large Cap ETFs were the biggest driver of growth, up $7.4 billion or 6%.

Sector ETFs also grew in August, up $5.0 billion or 8.4%. Inverse and Leveraged ETFs declined again in August, falling by $2.1 billion or 6.8%.

According to the ETF Directory, the biggest Large Cap ETF is the $76 billion SPDR S&P 500 (SPY).  Top holdings include ExxonMicrosoft, and JPMorgan Chase.