Yearpairs

Yearpairs are pairs of calendar or fiscal years used in temporal data analysis to compare measurements taken in different years. They can be formed as ordered pairs (y, y+τ) with a fixed lag τ, such as τ = 1 for consecutive years, or as unordered sets {y1, y2} chosen by criteria such as matching calendar periods or seasonal conditions.

In practice, yearpairs support calculations of year-over-year change, growth rates, and lagged correlations. Analysts decide whether to align by calendar year or fiscal year and how to handle leap years and missing data. When using (y, y+τ), the statistic of interest is computed on the pair, for example the change in an indicator Δ = value(y+τ) − value(y), or a normalized growth rate Δ/value(y).

Applications span economics, finance, climate research, public health, and education. In climate studies, yearpairs compare annual anomalies to assess year-to-year variability; in economics, they enable lagged indicators and forecasting. Yearpairs also facilitate cross-year comparisons of policy outcomes or program effects.

Examples include lag-1 yearpairs such as (2010, 2011) and lag-5 yearpairs such as (2005, 2010). Unordered yearpairs may be used to assess year-to-year similarity across different periods, for instance when evaluating years with similar macro conditions.

Limitations involve calendar irregularities, seasonality, leap year effects, data gaps, and non-stationarity, which can complicate interpretation. Clear documentation of the pairing scheme and the chosen lag are essential for reproducibility and proper inference.