From Sociological Images:
The dominant firms in the U.S. and other major capitalist counties are happily making profits, but they aren't interested in investing them in new plants and equipment that increase productivity and create jobs. Rather they prefer to use their earnings to acquire other firms, reward their managers and shareholders, or increase their holdings of cash and other financial assets.
The increase in profits has swamped the increase in investment over the relevant time period; in fact, investment in current dollars has actually been falling.
Looking at the ratio between these two variables helps us see even more clearly the growth in firm reluctance to channel profits into investment. The investment ratio (investment/profits) was 62% in 1971, peaked at 69% in 1979, fell to 61% in 2000 and 56% in 2008, and dropped to an even lower 46% in 2012.
According to Michael Burke, if U.S. firms were simply to invest at the level they did in 1979, not even the peak, the increase in investment in the American economy would exceed $1.5 trillion, close to 10% of GDP.