Tax Policy, the Interest Elasticity of Saving, and Capital Accumulation: Numerical Analysis of Theoretical Models
通过数值模拟分析减税对储蓄和资本形成的影响，发现此类模拟虽能揭示理论参数互动，但无法为减税刺激资本形成提供理论依据，强调经验数据只能来自实证研究。
Increasing disillusionment with traditional empirical methods is having major impact on research methodology, which is increasingly turning to simulation analysis based on theoretical and assumed parameter values. In research on saving and wealth accumulation, there have been several recent studies' consisting of simulation of theoretical based on cycle model. A particular focus has been tax policy and capital formation, which is area of concentration of this paper. The aim is to analyze in theoretical simulation context, impact on saving and wealth of an increase in after-tax rate of return to saving, generated by cut in tax rate on income from capital. This paper suggests that such simulation analysis, while instructive as to behavior of class of examined, and as to critical channels of influence, does not yield theoretical presumption in favor of cutting taxes on income from capital as means of stimulating capital formation. The development of this literature derives in part from disillusionment with traditional empirical methods; many such papers begin by listing litany of problems involved in usual type of empirical analysis before proceeding to simulation of theoretical structures. The implicit conclusion at times appears to be that because of daunting problems of standard empirical methodology, results derived from it can be ignored, and that empirical magnitudes can perhaps be discovered by deductive means. The temptation to think of precise numerical results derived from theoretical simulation as empirical can be rather strong; it needs to be reemphasized that empirical magnitudes can only be determined by empirical studies. In Section I, theoretical structure of cycle model2 is outlined, and several numerical simulations of this model are presented. These simulations highlight interesting and nontrivial interactions of theoretical parameters, and also demonstrate difficulty involved in attempts to develop robust aggregate implications from such framework. For instance, it is argued that Summers' claim to have developed a prima facie theoretical case for high interest elasticity of (1981a, p. 537) does not stand up to sensitivity analysis-a small change in assumed rate of pure time preference, or in other parametric assumptions, generate otherwise plausible cases in which the interest elasticity of aggregate saving is low. The experiments conducted in Section I are partial equilibrium in sense that interest rate is changed exogenously, which changes savings and hence capital stock, but feedback effect of capital *International Monetary Fund. This paper derives from chs. 2 and 3 of my doctoral dissertation, completed during Research Fellowship at Brookings Institution. Financial support was received from Brookings and Social Science Research Council. I am grateful to Henry Aaron, Barry Bosworth, Maxim Engers, Irwin Friend, Laurence Kotlikoff, Franco Modigliani, Joseph Pechman, Duncan Ripley, Robert Shiller, Patricia Stack, and my supervisor Albert Ando for comments and guidance on earlier drafts. None of above institutions or individuals is responsible for views expressed or any remaining errors. 'For example, see James Tobin and Walter Dolde; Betsy White; Lawrence Summers (1978, 1981a,b), G. Moore; Alan Auerbach and Laurence Kotlikoff; and Auerbach, Kotlikoff, and J. Skinner. 2It is popular to establish sharp dichotomy between life cycle models and bequest models. This taxonomy ignores frequent references to potential significance of in writings of originators of cycle hypothesis. A distinction between zero cycle models and life cycle incorporating bequests is more accurate in terms of doctrinal history. See for example, Albert Ando and Franco Modigliani, and Modigliani and Richard Brumberg.