Despite the stock market's upbeat sentiment around the potential for pro-growth policies under President-elect Donald Trump, history shows that, on average, the first year under a Republican administration hasn't been great for equities.

"Since WWII, the S&P 500 fell an average of 2.7% during the first year of a new Republican president's first term in office," Sam Stovall, chief investment strategist at CFRA, wrote in a note to clients Monday.

The strategist studied the market's quarterly performance during the first year of Republican administrations, and the findings weren't as encouraging as investors might have hoped.