1[2 {"id":"C1","text":"Over 1960Q1-2019Q4 the Okun coefficient is about -0.26 pp of unemployment per 1% quarterly real GDP growth, and its HAC 95% interval lies below zero.","results_keys":["effect_estimate","effect_se","hac_lags","effect_ci_low","effect_ci_high","conclusion","n_analysed"],"status":"supported","caveat":"Reduced-form, contemporaneous association; not causal; omits lagged growth."},3 {"id":"C2","text":"Real GDP growth substantially improves on a mean-only prediction of the change in unemployment (RMSE 0.325 -> 0.250 pp).","results_keys":["baseline_metric","model_metric"],"status":"supported","caveat":"In-sample fit only; no out-of-sample evaluation."},4 {"id":"C3","text":"The classical Chow test rejects equality of (alpha, beta) between 1960Q1-1983Q4 and 1984Q1-2019Q4 at the 5% level.","results_keys":["chow_f_stat","chow_p_value","stability_conclusion","n_sub1","n_sub2"],"status":"supported","caveat":"Classical test assumes iid errors; a HAC-robust Wald version (in sensitivity.json, not results.json) also rejects. Break date imposed, not estimated."},5 {"id":"C4","text":"The subperiod slopes are nearly identical (-0.259 vs -0.273), so the instability is driven by the intercept / break-even growth rather than by the Okun slope itself.","results_keys":["beta_sub1","beta_sub2","intercept"],"status":"supported","caveat":"Point estimates support it; the separate HAC tests of slope (p=0.85) and intercept (p=0.25) differences are reported in sensitivity.json, not in results.json; individually imprecise."}6]7