This paper studies asset pricing in a setting in which idiosyncratic risk in human capital is not fully insurable. Firms use long-term contracts to provide insurance to workers, but neither side can commit to these contracts; furthermore, worker-firm relationships have endogenous durations owing to costly and unobservable effort. Uninsured tail risk in labor earnings arises as a part of an optimal risk-sharing scheme. In the general equilibrium, exposure to the resulting tail risk generates higher risk premia, more volatile returns, and variations in expected returns across firms. Model outcomes are consistent with the cyclicality of factor shares in the aggregate, and the heterogeneity in exposures to idiosyncratic and aggregate shocks in the cross section.

This paper examines the reliability of widely used surveys on U.S. businesses. We compare survey responses of business owners with administrative data and document large inconsistencies in business incomes, receipts, and the number of owners. We document problems due to nonrepresentative samples and measurement errors. Nonrepresentativeness is reflected in undersampling of owners with low incomes. Measurement errors arise because respondents do not refer to relevant documents and possibly because of framing issues. We discuss implications for statistics of interest, such as business valuations and returns. We conclude that predictions based on current survey data should be treated with caution.

In this appendix, we provide details on the data sources and construction of variables for our analysis in "What Do Survey Data Tell Us about U.S. Businesses?" We also include the auxiliary tables and figures omitted from the main text.

We develop a theory of sweat equity—which is the value of business owners’ time and expenses to build customer bases, client lists, and other intangible assets. We discipline the theory using data from U.S. national accounts, business censuses, and brokered sales to estimate a value for sweat equity for the private business sector equal to 1.2 times U.S. GDP, which is roughly the value of fixed assets in use in these businesses. Although latent, the equity values are positively correlated with business incomes, ages, and standard measures of markups based on accounting data, but not with financial assets of owners or standard measures of business total factor productivity (TFP). We use our theory to show that abstracting from sweat activity leads to a significant understatement of the impacts of lowering tax rates on business incomes—on both the extensive and intensive margins. We also document large differences in the effective tax rates and the effects of tax changes for owner and employee labor inputs. Lower tax rates on owners results in increased self-employment and smaller firm sizes, whereas lower rates on employees has the opposite effects. Allowing for financial constraints and superstar firms does not overturn our main findings.