ETFs can also appeal to investors who want to play different sectors of the market and fill gaps in their diversified portfolios, says Demmissie. They now include almost every flavor, from ETFs that track bonds, real estate, commodities and currencies to niche offerings that can be country specific, socially responsible, or dividend- or fundamentals-weighted.
"What investors love about ETFs is they offer diversification, low cost and trading flexibility," says Michael Iachini, managing director of ETF Research at Charles Schwab Investment Advisory. "Stock and bond ETFs, the plain vanilla index-based funds, are pretty straightforward and are really not very different from mutual funds. They are extremely transparent, you can see what they hold, they are very well understood, and I think that investors are pretty comfortable with them."
But before you invest in ETFs, consider these key questions.
What does the ETF try to do?
"Some investors say, 'I want to buy ETFs. What ETFs have done well?' That is not the right way to approach it," says Iachini. "What you should do is say, 'OK, I want an ETF that buys small-cap stocks,' and then find out what ETFs pull that kind of stock."
Understand the investment goal of the ETF and how it is structured, he says. "Is it an index ETF? Most ETFs are, but there are some that are actively managed, so make sure you understand that. If it is an index, how is the index built? Is it a traditional market-capitalization-weighted index? Or equal-weighted, or fundamentals-weighted?"
An ETF's investment goal and underlying holdings can typically be found on the fund's website, updated daily, as well as historical returns and performance comparisons to the index.
What does the ETF cost?
While index mutual funds generally have low management fees, ETFs often have the edge, with operating expense ratios averaging 0.56 percent of assets compared to 0.98 percent for index mutual funds, according to Morningstar. The U.S.' first and still most popular ETF out there, State Street's SPDR S&P 500, costs just 0.09 percent. But investors need to consider total costs, which include trading fees.
ETFs often carry a commission upon buying and selling, so they may not make sense for investors who add to positions in small increments, as many people do in retirement funds or through dollar-cost averaging. However, a growing number of brokerages now offer commission-free ETFs, making them attractive even in these situations.