ETF Trends publisher Tom Lydon joined Jeff Macke of Yahoo Finance to discuss the strength of mid- and smal-cap exchange traded funds in 2015. As the U.S. dollar continues to strengthen against foreign currencies, large-cap companies with overseas revenue streams could see profits diminish.

However, more domestically-focused mid- and small-cap ETFs are beneficiaries of the strong dollar.

Mid- and small-cap companies tend to be U.S. focused and are more closely tided to the well being of the U.S. economy. With the U.S. economy on the rise and low energy prices fueling growth, smaller company stocks could continue to outperform.