We develop a dynamic macroeconomic model with heterogeneous financial intermediaries and endogenous entry. Time-varying endogenous macroeconomic risk arises from the risk-shifting behaviour of the cross-section of financial intermediaries. When interest rates are high, a decrease in interest rates stimulates investment and decreases aggregate risk. In contrast, when they are low, further stimulus can increase financial instability while inducing a fall in the risk premium. In this case, there is a trade-off between stimulating the economy and financial stability. This provides a model of the risk-taking channel of monetary policy.

We show that incorporating defined benefit pension funds in an incomplete markets asset pricing model improves its ability to match the historical equity premium and riskless rate and has important risk‐sharing implications. We document the importance of the pension fund's size and asset demands, and a new risk channel arising from fluctuations in the fund's returns. We use our calibrated model to study the implications of a shift to an economy with defined contribution plans. The new steady state is characterized by a higher riskless rate and a lower equity premium. Consumption volatility increases for retirees but decreases for workers.