For nearly 20 years, exchange-traded funds (ETFs) have been available to investors, offering diversification, liquidity and tax advantages, along with the tradability of a stock. ETFs are usually based on a number of asset classes, but can also be specialized to cater to individual strategies — such as leveraged long or short ETFs and actively managed funds.

So far in 2012, the stock market has been strong, with the S&P 500 up 7.9 percent. but many of the top ETFs have far surpassed that gain. Although experts an make a bull case or bear case for 2012, some of the top performing ETFs reflect broad market trends.

To get an idea of which ETFs have been the most successful, the CNBC.com analytics team pored through the 100-largest funds (based on assets under management) to see which had the best year-to-date performance. The funds in this group have market capitalizations between $2.2 billion and $73.3 billion. ETFs with a 10-day average volume less than 1 million shares were excluded. Prices and market capitalizations were calculated as of the market close on Feb. 22.

So, which ETFs have been the top performers so far this year? Click ahead to find out.