Even at near-zero interest rates for a prolonged period since the financial crisis, why has business investment in advanced economies remained persis-tently below its pre-crisis level? This paper investigates empirically the roots of this investment puzzle from the global megatrend perspective. The empir-ical model of this study augmented the uncertainty-finance accelerator in-vestment model with megatrend variables of a transition to service industry, ageing population and a rise in income inequality. The main estimation results show that they have affected negatively the business investment over the pe-riod 1980-2014. The shift-to-service driven investment fall is the price-dominant effect during the transition, which is not necessarily pessimistic news, while the suppressing effects from ageing and a rise in income inequali-ty require adequate policy reactions. In addition, the analysis finds significant negative spillover effects of trade partners’ ageing and income inequality on a country’s own private investment. Based on the empirical results, I expect that the G20’s efforts in inclusiveness with structural reforms will stimulate global business investment. Keywords: investment, megatrends, aggregate demand, uncertainty, G20, inclusiveness JEL classification: E20, F41, F42