Business investment has weakened across OECD economies in recent decades. Using firm-level data for 17 OECD countries over 2003–2022, this paper documents a marked decline in the responsiveness of tangible investment to firm productivity following the Global Financial Crisis, with only a partial recovery thereafter, pointing to a weakening of capital reallocation toward more productive firms. The decline is broad-based across countries and sectors, holds after accounting for intangible investment, and is confirmed under an instrumental-variables strategy. Both frontier and non-frontier firms experienced a reduction in responsiveness, though the decline is larger and more persistent among non-frontier firms, while frontier firms proved more resilient. Partial-equilibrium counterfactuals suggest that maintaining pre-crisis responsiveness would translate into substantially higher aggregate investment and measurable productivity gains. Policy and market conditions shape how strongly investment responds to productivity. Responsiveness is weaker in sectors where firms depend more on external finance and in countries with less efficient insolvency regimes, the latter most apparent at the frontier. More concentrated markets are associated with lower responsiveness, particularly among non-frontier firms, whereas greater trade openness is associated with stronger responsiveness across the productivity distribution.