اثر رشد غیر محتمل تحرک سرمایه جزئی: برخی از حساب نئوکلاسیکی

In the neoclassical growth model of Barro et al. [Am. Econ. Rev. 85 (1) (1995) 103–115], partial capital mobility across economies generates implausibly large growth effects under a standard parameterization of preferences and technology. Reasonable growth effects only occur if substantially less than the share of physical capital in factor income can serve as collateral for external borrowing. This finding confines the empirical relevance of the open-economy neoclassical growth model to the case of international capital flows, where market imperfections are likely to prevail. But for partial capital mobility across economies such as US states, where market imperfections appear less relevant, the model cannot produce plausible long-run growth effects.

The Solow-type neoclassical growth model with partial physical capital mobility by Barro et al. (1995) can explain why European regions or the US states, despite a high degree of internal capital mobility, exhibit a rather low rate of convergence to the steady state. The model assumes that physical capital can be financed by external borrowing because it can serve as collateral, but human capital must be financed by domestic savings. If the amount of external debt is constrained by the share of physical capital in factor income, the model predicts a rate of convergence both with and without capital mobility in the range of 2%. Holding constant the determinants of the steady state, such a rate of ‘conditional’ convergence has been estimated in numerous international cross section studies.1 The impact of partial mobility of capital on growth, as different from the impact on convergence, is a so far neglected aspect of the debt-constrained neoclassical growth model. Using the same parameterization of preferences and technology as Barro et al. (1995), I find that the predicted growth impact of partial physical capital mobility is implausibly large for economies not close to their steady state, i.e. for economies which have been growing fast in the past. My findings suggest that the neoclassical growth model only accounts for the transitional dynamics of fast growing open economies if the amount of external borrowing is limited to a minor fraction of the share of capital that can serve as collateral. This additional constraint may apply for the case of international capital flows, where market imperfections are likely to prevail. However, there is no obvious reason why, say, external borrowing of US states on the integrated US capital market should be limited to a minor fraction of the capital share that can serve as collateral. But without this assumption, the model does not predict plausible long-run growth effects of partial capital mobility for US states. This finding is robust to alternative parameterizations of preferences and technology. Hence the empirical relevance of the open-economy neoclassical growth model appears to be limited to cases where market imperfections can be utilized to reconcile theoretical predictions with observed growth rates.

For a standard parameterization of preferences and technology, a Solow-type neoclassical growth model cannot reconcile predicted growth effects of partial capital mobility with observed growth rates for a number of economies. The model only works for economies which are close to their steady state. But the model does not work for fast growing economies, i.e. for economies which grow by approximately 1 percentage point faster than the presumed rate of technological change. The model produces more plausible growth effects of capital mobility if less than the share of physical capital in factor income can serve as collateral for external borrowing. Capital market imperfections may thus explain why the model overestimates the growth effect of capital mobility for fast growing emerging economies. But capital market imperfections are difficult to motivate for the case of US states, which can borrow on an integrated US capital market. For fast growing US states, the model also overestimates the growth effect of capital mobility. The predicted implausible growth effects of capital mobility appear to be robust to a number of alternative parameterizations of preferences and technology. Substantial effects only arise for alternative parameterizations of factor shares, which can be used to model capital market imperfections. These findings limit the empirical relevance of the open-economy neoclassical growth model to the case of international capital flows, where market imperfections are likely to prevail. In the absence of capital market imperfections, the predicted growth effects of capital mobility are too large by an order of magnitude.