There has been a substantial amount of convergence between post-Keynesian and Marxist economics, the writings of Kalecki being commmon ground for both traditions. Still, some differences remain. While authors in both traditions seem to agree to a large extent on short-period issues, long-period matters relating to the role Of saving, the rate of profit, inflation, crowding out, excess money supply, are still contentious. All this seems to depend on the exact form taken by the investment function, more specifically the role of capacity utilization. Four different equations are set up to be tested, two of which correspond to two variants of the Marxist view, while the other two equations correspond to a naive and a sophisticated Kaleckian view, the latter being based on hysteresis. The equations are tested on three sets of annnal Canadian data. Various statistical tests are applied to all four equations in an effort to rank them, notably information and encompassing tests. The Kaleckian equation with hysteresis generally comes out empirically with the preferred statistical properties, when manufacturing data on actual rates of capital accumulation are considered separately or when both realized and intended rates of investment for the total industrial sector are used. © 2004 Taylor and Francis Ltd.