Book excerpt: Research report on various economic models of the income opportunities of older workers in the USA to investigate the effect on retirement decisions - examines the determinants of retirement (health, social security, occupational pension schemes, private sector assets); presents regression, discrete choice and nonparametric models to evaluate retirement age responses to a change in budget sets; reviews explanation of workers' retirement age preferences across a sample of ten pension schemes; includes simulations of effects of 4 social security reforms on retirees' income.