Life course and cohort measures Hist 5011

Cross-sectional data “Snapshot” of a population at a particular moment Examples: Census; Tax list Limitation: Often can’t tell characteristics of an individual prior to the occurrence of an event (e.g. effects of poverty on divorce for women)

Some data that is gathered over a period of time (e.g. wills, court records, guild membership lists) may be treated like cross sectional data

Longitudinal data Continuous or repeated observations about the same individuals Allows analysis of the sequence of events Survey data  Panel studies (e.g. PSID)  Repeated waves (NSFH, Add Health)

Historical Longitudinal Data Linked censuses or status animarum Population registers (esp. Netherlands, Belgium) Genealogies (esp. Asia). Family reconstitution: linked baptism, marriage, and death records

Cohort Analysis Follow a group of people through successive cross-sections as they age Usually defined by cohort of birth Can also use marriage cohorts, educational cohorts, etc.

Example: percent of native-born whites residing outside state of birth, Total

Highlight the same group over time Total

Rearrange into birth cohorts Year of birth

Make a nice graph

Synthetic cohorts Similar to cohort analysis, but instead of using successive observations of the same group of people, you treat the age distribution of the population as if it were a cohort passing through time. Yields different result from true cohort analysis in periods of rapid change Synthetic cohorts are the basis of most commonly used measures of demographic behavior (e.g. life expectancy, total fertility rate, and median age at marriage.

Synthetic cohorts for internal migration Total

... And make a nice graph

Period change vs. cohort change vs. life course change Period change refers to changes that occur from one year to the next Cohort change is change occuring between successive birth cohorts Often the two are different (example of fertility in the depression) Life course change is change that occurs within a cohort as they age.

Period change: percent migrant among persons aged 55-59

Demographic synthetic cohort measures Life expectancy: derives from life table; 2000 represents the number of years that would be lived by a synthetic cohort that experienced the same age-specific death rates as the population as a whole in 2000 Does not mean how long a baby born in 2000 can expect to live There never has been and probably never will be a cohort that experiences the same age pattern of death Cohort life tables are possible, but only for cohorts that are extinct.

Total fertility rate Age-specific fertility rate is the number of births divided by the number of women at each age; or, the mean number of children born to women of each age in the course of a year (e.g., 2000). Total fertility rate is the sum of the age-specific fertility rates over all ages Total fertility represents the number of children that would be born to a hypothetical cohort that went through life experiencing the ASFRs of a particular period (assuming that none of them died before the end of their childbearing years)

Indirect Median age at first marriage Another synthetic cohort measure Make a graph of percent ever-married in a census year, and find the point at which half of those who will ever marry have married

Other synthetic cohort measures Years of schooling: from school attendance Age at leaving home. But what if they come back? Age at starting work, retiring, any transition that most people go through and usually do not return Years with any characteristic

Years Lived Before Age 80 With Family and as Unrelated Individual, assuming no mortality: Synthetic cohorts in 1880, 1940, and 1950

Same thing, adjusting for mortality