policyengine-period-patterns

Use period.this_year to read YEAR-definition variables within MONTH formulas. This Golden Rule pattern ensures correct period-specific access without manual conversion, enabling monthly eligibility checks that depend on annual demographics, assets, or income data.

Stock variables (assets, counts, booleans) use period.this_year for YEAR access; flow variables (income-like metrics) use period directly. Proper handling prevents misalignment when monthly formulas reference annual definitions or vice versa across demographics and financial metrics.

Apply explicit period conversion patterns documented in this Skill to align monthly-calculated values to YEAR definitions. The conversion handles demographics, assets, counts, and income-flow metrics, ensuring consistent period-specific variable access in both directions.

Yes. Period conversion patterns enable MONTH formulas to read annual demographics using period.this_year, supporting monthly eligibility determination that depends on annual-definition data without manual aggregation or period misalignment.

Age, assets, counts, and booleans are stock-type variables using period.this_year for consistency within a year; income-like variables are flow-type using period directly. This distinction prevents double-counting and ensures semantically correct period-specific calculations across PolicyEngine formulas.

Without explicit conversion, variable values misalign across periods, causing incorrect eligibility outcomes and metric calculations. This Skill documents common MONTH-to-YEAR and YEAR-to-MONTH access patterns and auto-conversion guidance to prevent these issues in demographic, asset, and income-flow contexts.