The Dow Jones Industrial Average is flirting with the 23,000 mark. If or when it reaches this level, it would mark yet another milestone for the index. Since the presidential election, the Dow is up 24 percent, the S&P is up 19 percent, and the Nasdaq has returned 24 percent. Terry Simpson, Director for BlackRock's Global Investment Strategy team, says despite the bull market, the firm is tempering expectations due to geopolitical risks. Simpson says GDP growth, tax reform structure, and other factors are going to have a hand in the economy's overall heath.