As the stock market rally continues higher and the 10-year Treasury yield nears a three-year high, investors ponder what yield level will bite stocks. Historically, the stock market has withstood much higher yields. Is a 3% bond yield a stop sign for equity investors? Or, with synchronized global growth and earnings results juiced by tax cuts, will it take a 4% or 5% 10-year bond yield before the stock market succumbs?