For most older people in the United States, Social Security is the major source of income: nine out of ten people age 65 or older receive benefits, which represent an average of 41 percent of their income. Largely as a result of Social Security, poverty rates for the elderly are at an all-time...

Data with which to study disability dynamics usually take the form of successive current-status measures of disability rather than a record of events or spell durations. One recent paper presented a semi-Markov model of disability dynamics in which spell durations were inferred from sequences of...