Turning now to table 13, we wish to explore a number of auxiliary hypotheses and to derive a more parsimonious set of productivity gap interactions. Regression 6 restricts the effects of human capital and the level of R&D capital to be zero. The productivity gap and change in R&D capital remain significant, and the restriction cannot be rejected (F(1,220)=0.69 [P=0.41]). Note that the absence of levels effects in human capital and R&D imply that the steady-state level of relative TFP is determined simply by the industry fixed effects and the catch-up rate. It has often been argued that there was a major structural break in Japanese growth in 1973 (see Denny et al., 1992, for example). In order to test this hypothesis, regression 7 includes break terms for 1973 for both the productivity gap and the change in log R&D. The change in both the productivity gap effect and in the R&D effect is negative but insignificant. The joint hypothesis of no structural break in these two variables cannot be rejected (F(2,219)=0.22 [P=0.80]).