Does financial wealth drive the share of risky assets in the portfolios of individual investors? Is the financial wealth elasticity of the risky share homogenous across investors or does it vary with their demographic, financial and portfolio characteristics? How does the aggregate demand for risky assets respond to changes in the wealth distribution? In portfolio choice theory, mechanisms such as habit formation, borrowing constraints, decreasing relative risk aversion, portfolio insurance, or a “capitalist” taste for wealth, all imply that richer households allocate a higher fraction of their financial wealth to risky investments. These theories also predict that the financial wealth elasticity of the risky share should vary with household characteristics, including financial wealth itself. Furthermore, a growing literature investigates how at the aggregate level, the demand for risky assets relates to the distribution of household preferences and characteristics.
The empirical household finance literature provides only partial evidence on these mechanisms. In cross-sections, richer and more educated investors are known to allocate a higher proportion of their financial wealth to risky assets than less sophisticated households (e.g. Campbell 2006; Calvet Campbell and Sodini, “CCS” 2007, 2009a, 2009b). In addition, the risky share has a negative cross-sectional relation to real estate holdings (Cocco 2005, Flavin and Yamashita 2002), leverage (Guiso Jappelli and Terlizzese 1996), and internal consumption habit (Lupton 2002). It is unclear, however, whether these variables directly impact portfolio choice, or simply proxy for latent traits such as ability, genes, risk aversion, or upbringing. Several recent papers suggest that panel data offer a possible solution to this identification problem when the characteristic of interest exhibits sufficient time variations (e.g. Brunnermeier and Nagel 2008, CCS 2009a, Chiappori and Paiella 2008). One difficulty with the dynamic panel approach is that the researcher needs to control for household inertia by using instruments, and the results are sensitive to the validity of the instruments.