The U.S. exchange-traded product market plowed ahead with relentless force in 2014 to close the year with assets greater than $2 trillion, or 18 percent more than the prior year.

According to figures from BlackRock, parent company of the iShares family of exchange-traded funds, U.S.-listed ETP inflows hit $52.6 billion in December. That marked the first-ever back-to-back months of asset inflows of at least $40 billion, and was fueled in part by the Federal Reserve’s investor-friendly monetary policy and steady U.S. economic growth.

iShares, State Street and Vanguard maintained their stranglehold on top of the U.S. leader board with 37.9 percent, 22.7 percent and 21.3 percent of market share, respectively. Invesco PowerShares comfortably remains number four (4.9 percent), while none of the rest of the top 10––Wisdom Tree Investments; First Trust Portfolios; Guggenheim; Charles Schwab; ProShares; and Van Eck Global––individually have more than 2 percent market share.

Beyond the top 10, 57 other U.S. fund providers in aggregate accounted for 4.6 percent of market share.

The three funds with the biggest inflows last year all had a similar theme: the SPDR S&P 500 (SPY), iShares Core S&P 500 ETF (IVV) and Vanguard S&P 500 (VOO) funds. The top––or bottom––three in terms of outflows (in descending order) were the PowerShares QQQ (QQQ), iShares MSCI Emerging Markets ETF (EEM) and SPDR Gold (GLD) funds.