The ETF business is top-heavy in terms of the biggest funds and the largest providers’ market share.

Together, the three biggest ETF sponsors — BlackRock’s (NYSE: BLK) iShares, State Street (NYSE: STT) and Vanguard — control more than 80% of the industry’s assets.

The U.S. marketplace is comprised of 1,443 exchange traded products from 51 sponsors with $1.27 trillion in total assets, according to XTF.

The two largest ETFs, SPDR S&P 500 (NYSEArca: SPY) and SPDR Gold Shares (NYSEArca: GLD), together account for nearly $200 billion.

In ETFs, the rich seem to get richer because of the traditional first-mover advantage. Investors also tend to gravitate to the largest and most liquid funds. However, an ETF’s liquidity is influenced by other factors aside from trading volume. [ETF Liquidity More Than Just Trading Volume]