Middle-capitalization stocks and asset category exchange traded funds are leading the charge as investors focus on companies better positioned to capitalize on continued U.S. growth.

For instance, the iShares Core S&P Mid-Cap ETF (NYSEArca: IJH) and SPDR S&P MidCap 400 ETF (NYSEArca: MDY) were up 3.8% year-to-date. In contrast, the e iShares Russell 2000 ETF (NYSEArca: IWM) rose 2.0% and SPDR S&P 500 ETF (NYSEArca: SPY) increased 2.2%.

Additionally, investors are not limited to the broad market-capitalization-weighted mid-caps. For example, the WisdomTree MidCap Dividend Fund (NYSEArca: DON), which focuses on dividend stocks, has also gained 3.5% year-to-date. The factor-based Powershares DWA Momentum Portfolio (NYSEArca: PDP), which includes a 49.9% tilt toward mid-caps and 46.5% toward large-caps, advanced 4.2% so far this year.

The rotation into mid-caps is fueled by perceived currency risks that large-caps are exposed to – large multi-national U.S. corporations may see revenue streams diminish as overseas currencies continue to depreciate against the U.S. dollar. [Strong U.S. Dollar Could Pressure S&P 500 Earnings, ETFs]

“Large investors have started to rotate funds and decrease their exposure to the S&P on the perception mid-caps have less reliance on multinational sales,” John Stoltzfus, chief investment strategist at Oppenheimer, said in a CNBC article. “It’s also a favorable space to find candidates for potential acquisitions when large-cap companies have shown a preference for M&A rather than organic growth.”

Stoltzfus points out that mid-cap names allow investors to diversify portfolios if they rode the rally in large-caps last year. Mid-caps also offer growth opportunities as some of these companies could become tomorrow’s large-cap brands.