ارتباط بین سهام عامل و توسعه اقتصادی

The stability of factor shares has long been considered one of the “stylized facts” of macroeconomics. Most factor share studies, however, acknowledge only two factors of production (total capital and total labor), which yields misleading results. I distinguish between reproducible and non-reproducible factors of production. I disentangle physical capital’s share from natural capital’s share and human capital’s share from unskilled labor’s share. Results reveal that non-reproducible factor shares decrease with the stage of economic development, and reproducible factor shares increase with the stage of economic development. This evidence suggests that studies relying on the macroeconomic paradigm of constant factor shares should be revisited. The evidence also supports endogenous growth models that allow technical progress to manifest itself via changes in factor shares.

Some factor share studies, such as Gollin (2002), present empirical evidence suggesting that factor shares are unrelated to output per worker. Others, such as Zuleta (2008a), conclude that factor shares vary systematically across countries. Despite conflicting empirical evidence and despite the doubts about the constancy of factor shares expressed by Keynes (1939) and Solow (1958), most researchers accept the claim that factor shares are constant, which was made by Phelps Brown and Weber (1953) and reiterated by Kaldor (1961), as a “stylized fact” of macroeconomics. As a result, the standard assumption in studies involving aggregate production functions is that capital shares and labor shares are constant over time and across countries and equal to 1/3 and 2/3, respectively. Factor shares are not constant across countries when factors of production are properly defined and measured. The key step is making a distinction between reproducible factors and non-reproducible factors. In most factor share studies, only two factors of production, capital and labor, are acknowledged. I show that failure to acknowledge more than two factors yields results and conclusions that are misleading at best.

Researchers estimating factor shares rarely make a distinction between reproducible and non-reproducible factors. As a result, the shares that are typically considered are composite shares that conflate the fractions of income paid to fundamentally different factors of production. A very common approach is to combine all factors of production into one of two categories: capital or labor. The standard capital share measure conflates physical capital’s share and natural capital’s share. The standard labor share measure conflates human capital’s share and unskilled labor’s share. Failure to acknowledge the composite nature of these standard share measures often leads to the conclusion that factor shares are constant across countries. My results reveal that the relationship between composite shares and the stage of economic development is different from the relationship between a single, non-reproducible or reproducible share and the stage of economic development. I find that non-reproducible factor shares decrease with the stage of economic development, and reproducible factor shares increase with the stage of economic development. This suggests that factor shares should be treated as variables rather than constant parameters. Studies that incorporate the assumption of constant factor shares should be revisited.