The expanding universe of exchange-traded funds is like an investment smorgasbord enabling investors to sample items ranging from the exotic (Nigerian stocks, anyone?) to the commonplace (such as the numerous ways to play the S&P 500).

Given the range of investment options among ETFs and their ease of use, it’s no wonder they’ve become a big hit with retail investors. According to the 2013 ETF Investor Study by Charles Schwab, 9% of respondents said they now hold 50% or more of their portfolios in ETFs. That’s more than double the 4% seen last year.

In addition, more than half of respondents said they plan to boost their ETF holdings over the next year. That’s 22% more than those who said the same thing last year.

Schwab surveyed more than 1,000 individual investors between the ages of 25 and 75 with at least $25,000 in investable assets. These folks, all of whom bought ETFs in the past two years or are considering purchasing them in the next two years, said the top benefit of ETFs is their ability to be bought and sold like stocks. 

Fifty-three percent of respondents said ETFs are best suited for long-term investors, while 40% said ETFs are well suited for active traders.