Description
Floor (birthYear-originYear)/cohortWidth for cohortIndex and return the corresponding lower year and excluded upper year.
Longitudinal ageing research links observations to people, waves, and sources. A person may appear in multiple records, so distinct-person coverage and record counts answer different questions and require explicit duplicate rules.
Floor (birthYear-originYear)/cohortWidth for cohortIndex and return the corresponding lower year and excluded upper year.
When to use this tool
Use Pension Study Birth Cohort Index when you need a record-coverage or source-support diagnostic in ageing research.
How to use the tool and how it works
- Enter birthYear, originYear, cohortWidth. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read cohortIndex, lowerYear, upperYearExclusive. Use the output convention below.
Require positive integer cohortWidth. Floor (birthYear-originYear)/cohortWidth for cohortIndex and return the corresponding lower year and excluded upper year.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| birthYear | Birth Year | Required. Safe integer. |
| originYear | Origin Year | Required. Safe integer. |
| cohortWidth | Cohort Width | Required. Safe integer; minimum 1. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| cohortIndex | Cohort Index | Required. Safe integer. |
| lowerYear | Lower Year | Required. Safe integer. |
| upperYearExclusive | Upper Year Exclusive | Required. Safe integer. |
{
"input": {
"birthYear": 1958,
"originYear": 1950,
"cohortWidth": 5
},
"output": {
"cohortIndex": 1,
"lowerYear": 1955,
"upperYearExclusive": 1960
}
}Limitations and assumptions
- Birth years before origin can yield negative indexes; this numeric cohort convention does not establish a pension rule, eligibility, or validated birth date.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Review the original study design, identifiers, and missing-data definitions. Use the full longitudinal dataset for inference rather than treating a local coverage flag as evidence of representativeness.
References
Similar or alternative tools
- Cohort Age Period Birth Year Identity
Return periodYear-ageYears and subtract recordedBirthYear for identityResidual.
- Cohort Period Index Gap
Subtract cohortIndex from periodIndex using exact integer intermediates before numeric export.