U.S. stocks are doing well, but European stocks are doing even better. The CAC and DAX are up more than 15 percent since the beginning of the year.
Eric Ristuben, Chief Investment Strategist at Russell Investments, believes it may be time to start adding European stocks as part of a multi-asset portfolio.
"Data out of Europe is getting better, and that continues to help European stocks," Ristuben told CNBC's "Power Lunch" on Friday.
Other positive factors include a weak euro, the start of the European quantitative easing program and "negative German bond yields," Ristuben said.