Crise, fall in the rate of return, and undercomsumption

Marx, in his book the Capital. predicted the collapse of capitalism on two ground. First, he stated that the rate of return will tend to fall as capitalism progress. This idea arouse from the observation that the returns were much higher in the XVI century than in the XIX and economists such as Ricardo or Smith agreed on this. Marx is innovative since he offered an explanation of this fall of returns: with scientific development, you need higher and higher investments to have the same return.
This idea of the falling rate of return was generally overlooked,. but was taken very seriously by the importan economist Schumpeter. He said that the fall of returns can be offset by innovation, which alters the organic composition of capital. We are in an age of general capitalist crissi, but return are faboulously high given the high rate of innovation due to infomration technologies.

The second mechanism pointed out by Marx is underconsumption. In the capitalist system, capitalist tend to pay labour force as little as possible, but this means that the base of consumer, which is composed mainly of laborer, shrinks progressively, leading to a crisis of underconsumption. The cires of 2009 was largely a crise of underconsumption.
The route to escape this contradiction was devised by John Maynard Keynes. If the economy as a whole ha a high rate of debt, debt compensates the low level of consumption. This trick worked wonderfully from 1945 to 2008, but, I dare say, it begins not to work any more. The level of public debts is astronomica in advanced countries, and begins to rise also in conutries licke China and Saudi Arabai, and there is probably a limit that cannot be trespeassed.

Anyway, it is amazing how the ideas of Marx have been taken  seriously by capitlamis economy, when they are usually dismissed as nonscientific in the divulgation.