Human Capital and Popular Investment Advice
Popular investment advice recommends that the stock/bond and stock/wealth ratios should rise with investor risk tolerance and investment horizon respectively, prescriptions that are difficult to reconcile with the simple mean-variance model. We show that extending the mean-variance model to include human capital, without any other modifications, can simultaneously justify both recommendations, so long as the correlation between labour income and stock returns falls within a range determined by market and investor-specific parameters. Aggregate labour income data from 11 countries generally satisfy this requirement, as do plausible individual income processes. We also consider the implications of human capital for the optimal bond/wealth ratio over the investment horizon, and examine the sensitivity of the stock/bond mix to the volatility of labour income.