The bears argue that stocks already reflect years of future profit gains. Remember, though, that even the best investors find it nearly impossible to time the market to catch the lows and highs. The U.S. economy is expected to grow 1.5 percent this year, then 3.4 percent in 2015, according to Congressional Budget Office estimates released Wednesday. Torsten Slok, chief international economist at Deutsche Bank Securities, notes that the short-term rates that helped drag stocks down at the end of the last seven bull markets were all higher than 4 percent. With the Fed holding those rates near zero, it could take many hikes for borrowing costs to rise enough to cause damage. Companies in the S&P 500 have spent $1.9 trillion on buybacks since the bull market began in March 2009, according to Howard Silverblatt, a senior index analyst at S&P Dow Jones Indices. By creating more demand for stocks, buybacks have kept prices rising even as others sell. Mutual funds, investment brokers, foreigners and pension funds have been net sellers of stocks over most of the last five years, according to the Fed. Since the end of World War II, the average is 18.3. The Fed may be able to raise rates slowly without damaging the economy and stock markets. The consumer price index is up 2 percent in the past 12 months, roughly equivalent to the Fed's target. David Levy, an economist, predicted the last U.S.