We theoretically characterize the behavior of machine learning asset pricing models. We prove that expected out-of-sample model performance---in terms of SDF Sharpe ratio and test asset pricing errors---is improving in model parameterization (or "complexity''). Our empirical findings verify the...

We explore the economic effects of biodiversity loss by developing an ecologically-founded model that captures how different species interact to deliver the ecosystem services that complement other factors of economic production. Aggregate ecosystem services are produced by combining several...