# Contract — F6-conf-03

Question. How strongly does the quarterly change in the US unemployment rate respond to quarterly real GDP growth (Okun's law, difference form), 1960Q1–2019Q4, and is the response stable across 1960Q1–1983Q4 vs 1984Q1–2019Q4?

Estimands. β (and α) in Δu_t = α + β g_t + ε_t, OLS; u_t = mean of 3 monthly UNRATE values; g_t = 100·Δln GDPC1 (quarterly, not annualised). Meaningful as a reduced-form conditional-mean association (not causal), under stationarity of (Δu, g) within the sample and a linear, time-invariant relation (the latter is tested). Uncertainty: Newey–West HAC (Bartlett) SE for full-sample β, 95% CI (normal critical value). Stability: subperiod OLS slopes and classical Chow SSR F-test, df (2, n−4).

Outputs. out/results.json (keys: sample_start, sample_end, n_sub1, n_sub2, baseline_metric, model_metric, effect_estimate, intercept, effect_se, hac_lags, effect_ci_low, effect_ci_high, beta_sub1, beta_sub2, chow_f_stat, chow_p_value, stability_conclusion, conclusion, task_id, feasibility, feasibility_reason, data_issues, n_input_rows, n_analysed, random_seed); out/figure1.png; out/table1.csv (period,n,intercept,slope,slope_se; 3 rows); out/report.md (6 sections); out/analysis.py; out/claims.json; plus state ledgers and exclusions.csv.

Information rules. Only data/GDPC1.csv and data/UNRATE.csv. Sample 240 quarters 1960Q1–2019Q4; 1959Q4 levels used for the first differences; nothing after 2019Q4 enters any estimate.

Invalidity / impossibility. Missing monthly UNRATE or GDPC1 values within 1959Q4–2019Q4; sample not equal to 240 quarters; using post-2019 data; non-HAC full-sample SE.