Casual Contraception in Casual Sex
Supplement A: Does the choice of school random vs. fixed effects matter?

Supplemental Table A1. Selected Odds Ratios Comparing Variants of Equation 2: School-Random-Effects vs. School-Fixed-Effects
Models Estimating the Odds of Coitus Models Estimating the Odds of Condom Use
School Random Effects School Fixed Effects School Random Effects School Fixed Effects
WomenMenWomenMenWomenMenWomenMen
Year of College
Freshman Year
Sophomore Year1.29***1.53***1.26**1.54***0.68**0.62*0.70**0.62*
Junior Year1.79***1.53***1.72***1.53***0.72**0.63*0.73*0.61*
Senior Year2.09***2.27***2.00***2.28***0.63***0.62*0.66***0.58**
Observations71443131714431312582125225821251
Supplemental Table A2. Selected Odds Ratios Comparing Variants of Equation 3: School-Random-Effects vs. School-Fixed-Effects
Models Estimating the Odds of Coitus Models Estimating the Odds of Condom Use
School Random Effects School Fixed Effects School Random Effects School Fixed Effects
WomenMenWomenMenWomenMenWomenMen
During/After Freshman Year
First Year of College
Years 2/3/4 of College1.31*1.371.36*1.38^0.51**0.36*0.51**0.40*
Mother's Educational Attainment
Mother Received a High School Education or Less
Mother Received Some College Education0.830.720.830.730.900.46^0.850.51
Mother Received a Bachelor's Degree0.880.770.900.790.730.740.710.81
Mother Received a Graduate Degree0.820.58**0.840.60*0.55*0.35*0.54*0.35*
Grade × Mother's Educational Attainment
Years 2/3/4 × Some College1.031.311.031.301.022.35^1.101.97
Years 2/3/4 × Bachelor's Degree0.831.310.841.301.221.511.251.35
Years 2/3/4 × Graduate Degree1.001.401.041.401.92*2.94*1.86*2.67*
School Gender Composition
≤ 53% Female
≥ 53% Female1.141.061.001.001.051.211.001.00
≥ 53% Female × Years 2/3/41.50***0.971.48***0.981.130.861.200.80
Observations71443131714431312582125225821251