The big debate raging right now is whether stocks can continue marching higher despite sky-high valuations. The doubters correctly point out that the S&P 500's breakneck 35% return since the April low has lifted its forward price to earnings ratio—a standard valuation measure—to stratospheric levels. According to FactSet, the S&P 500's forward one-year P/E ratio, which divides the S&P 500's price by the collective earnings anticipated over the coming year, stands at 22.8, handily above the 10-year average ...