## Age, Period and Cohort Effects for Vital Rates

### Description

Number of prostate cancer deaths and midperiod population for nonwhites in the USA by age and period.
The cohort index `k`

is related to age and period indices (`i`

and `j`

, respectively) by `k = j + I - i`

,
where `I = max(i)`

(Holford, 1983, Table 2).

### Usage

`data(cohorts)`

### Format

A data frame with 49 observations on the following 4 variables.

- period
A factor with levels `1935-`

, `1940-`

, ..., `1965-`

.

- age
A factor with levels `50-`

, `55-`

, ..., `80-`

.

- y
Numeric: the number of prostate cancer deaths.

- n
Numeric: the midperiod population size.

### References

Holford, T.R., 1983. *The estimation of age, period and cohort effects for vital rates*. Biometrics 39, 311-324.