The Emperor Has No Cash Flows

Why Factor Models Fail with Private Assets in TPA

Abstract

The Total Portfolio Approach (TPA) promises to deliver sustainably higher returns by treating
public and private assets on equal footing. Risk model vendors promote factor models as the
unifying framework that delivers this. Yet the mathematical elegance builds on a fundamental
misunderstanding of private market investing. Commercial factor models reduce private fund
commitments to collections of factor loadings such as market beta, size, value, and momentum.
This approach renders invisible the very characteristics that define these investments: their cash
flow dynamics, their illiquidity by design, and their operational requirements. This paper argues
that the dominant approach of applying factor models in TPA is not just incomplete but misleading,
offering asset owners a false sense of analytical precision while obscuring the real constraints
and opportunities in private market allocation. The alternative exists: sophisticated investors
already use cash flow models to answer the questions that actually matter: commitment pacing,
liquidity management, and allocation sizing.