Thomas Piketty's new book Capital in the Twenty-First Century (2014) has been a stunning success. This is not surprising. It brilliantly documents long-term trends in wealth ownership and income distribution in advanced economies. In particular, it shows how the share of income accruing to wealth-owners has increased dramatically in recent decades2 . It also provides a simple explanation of this development based on the standard neoclassical theory of factor shares. This theory establishes a link between the capital intensity of production and the share of profits in total output. The nature of this link depends on the elasticity of substitution between capital and labour. When this elasticity is greater than unity, an increase in the capital-output ratio leads to an increase in the share of profits. This, in essence, is Piketty's explanation for the increased share of wealth-owners in national income. Thus, the shift in income distribution is due to the over-accumulation of capital: there has been too much real investment
The above explanation has two related flaws. Piketty's assumption regarding the elasticity of substitution is not correct. There is considerable evidence that this elasticity is less than unity. Moreover, Piketty's method for measuring changes in the capital-output ratio is misleading. He fails to allow for the disproportionate increase in the market value of certain real assets, especially housing, in recent decades. This leads him to conclude, mistakenly, that the capital-output ratio has risen by a considerable amount. In fact, conventional measures of this ratio indicate that it has been either stationary or has fallen in most advanced economies during the period in question. This would suggest that the basic problem is not the over-accumulation of capital, but just the opposite. There has been too little real investment.
Robert Rowthorn | Faculty of Economics, University of Cambridge
No comments:
Post a Comment