

Vanguard and Fidelity research suggests that U.S. small-cap stocks might keep outperforming large-cap stocks. Two popular small-cap ETFs have both outperformed the S&P 500 and Nasdaq-100 in the past year.

AIA Group Ltd increased its position in iShares Russell 2000 ETF (NYSEARCA:IWM) by 181.5% in the undefined quarter, according to the company in its most recent 13F filing with the Securities and Exchange Commission (SEC). The firm owned 1,864,118 shares of the exchange traded fund's stock after buying an additional 1,201,808 shares

Allspring Global Investments Holdings LLC lifted its stake in iShares Russell 2000 ETF (NYSEARCA:IWM) by 110.3% during the first quarter, according to its most recent 13F filing with the Securities and Exchange Commission (SEC). The fund owned 259,801 shares of the exchange traded fund's stock after buying an additional 136,243 shares during

Small-Cap stocks have been some of the market's strongest recent performers, with year-to-date returns for the Russell 2000 Index up approximately 20%.

Small caps have been having a banner year, with the Russell 2000 outperforming the S&P 500 year-to-date. Some small-cap focused ETFs have also surpassed that benchmark.

If you hold the iShares Russell 2000 ETF (NYSEARCA:IWM), you already know it as the default small-cap ticker on every financial channel.

As popular as index funds are, they have a few shortcomings.

The iShares Russell 2000 ETF (IWM) holds nearly 2,000 small-cap stocks across different sectors. Small-cap stocks tend to be more volatile because they're more susceptible to broader economic conditions.