FERTIL3.DES gfr pe year t tsq pe_1 pe_2 pe_3 pe_4 pill ww2 tcu cgfr cpe cpe_1 cpe_2 cpe_3 cpe_4 gfr_1 cgfr_1 cgfr_2 cgfr_3 cgfr_4 gfr_2 Obs: 72 1. gfr births per 1000 women 15-44 2. pe real value pers. exemption, $ 3. year 1913 to 1984 4. t time trend, t=1,...,72 5. tsq t^2 6. pe_1 pe[t-1] 7. pe_2 pe[t-2] 8. pe_3 pe[t-3] 9. pe_4 pe[t-4] 10. pill =1 if year >= 1963 11. ww2 =1, 1941 to 1945 12. tcu t^3 13. cgfr change in gfr: gfr - gfr_1 14. cpe pe - pe_1 15. cpe_1 cpe[t-1] 16. cpe_2 cpe[t-2] 17. cpe_3 cpe[t-3] 18. cpe_4 cpe[t-4] 19. gfr_1 gfr[t-1] 20. cgfr_1 cgfr[t-1] 21. cgfr_2 cgfr[t-2] 22. cgfr_3 cgfr[t-3] 23. cgfr_4 cgfr[t-4] 24. gfr_2 gfr[t-2]