NEW YORK ( TheStreet) -- Investing in bonds has proven to be a home run for 30 years, but the bubble is primed to pop. The BarCap U.S. Government Aggregate Treasury Index has had an average annual return of 8.5% over three decades. Bonds' gains accelerated during the Great Recession, performance that attracted inflows. In fact, since April of last year, new money flowing into bond funds has far outpaced that of equity funds. Going back further, bonds have benefited from the tailwind of falling interest rates since the Reagan administration in the 1980s. With yields on the benchmark Treasury bond now near record lows -- around 2% -- any increase will spell losses for investors.