We propose an organizing framework that determines asset prices by equating household sector asset demand derived from an economic model to the observed supply of assets provided by other sectors. We then use a specific model of household asset demand to decompose historical changes in asset positions into changes in new asset supply and household income, as well as changes in return expectations. Our findings show that supply and income changes are important determinants of the wealth-to-GDP ratio and real estate positions, and return expectations are the key determinant of equity positions. (JEL: G11, G12, E44, E21)