An understanding of the origins of earnings distribution is of central importance for any public policy which has the aim of combating economic inequality. This book tries to provide some theoretical foundations that could serve as a rational basis for such policies. The approach, strongly influenced by human capital theory, is especially novel in that it permits individual analyses at three interconnecting levels of aggregation using the same basic microeconomic model: the level of the overall earnings distribution across all age groups; and the distribution of lifetime earnings. The analysis demonstrates the interdependence between age composition, inequality, and public distribution policy. It provides economic interpretations of empirical findings and identifies several policy conflicts. It also addresses the question of how differences between individuals are transformed into income differences.