Table 1 Descriptive statistics

General breastfeeding measures

 Breastfed (y/n)

6600

0.445909

3388

0.436836

3212

0.45548

 Total duration (In weeks)

2784

21.39332

1408

21.6108

1376

21.17078

Duration targets (y/n)

 6 weeks

2784

0.700072

1408

0.697443

1376

0.702762

 6 months

2784

0.282687

1408

0.291193

1376

0.273983

 1 year

2784

0.077227

1408

0.081676

1376

0.072674

Season of birth

 Winter

6877

0.24342

3522

0.249574

3355

0.23696

 Spring

6877

0.239494

3522

0.229983

3355

0.249478

 Summer

6877

0.265668

3522

0.266326

3355

0.264978

 Fall

6877

0.251418

3522

0.254117

3355

0.248584

Race/ethnicity

 Non-black/non-Hispanic

6877

.452232

3522

0.454571

3355

0.449776

 Black

6877

0.332122

3522

0.327371

3355

0.337109

 Hispanic

6877

0.215646

3522

0.218058

3355

0.213115

Education level

 High school dropout

6876

0.128126

3521

0.131213

3355

0.124887

 High school

6876

0.502909

3521

0.499006

3355

0.507005

 Associates

6876

0.118819

3521

0.118432

3355

0.119225

 Bachelors

6876

0.123473

3521

0.123544

3355

0.123398

 Graduate

6876

0.055701

3521

0.055098

3355

0.056334

 Other degree

6876

0.070972

3521

0.072707

3355

0.069151

Test score

 ASVAB math score

6490

3562.08

3329

3621.49

3161

3499.51

Age of mother at birth

 10–19

6877

0.184964

3522

0.186542

3355

0.183309

 20–29

6877

0.577287

3522

0.580068

3355

0.574367

 30+

6877

0.23775

3522

0.23339

3355

0.24232

Mother’s lifestyle factors at the birth of the child

 Hours worked for pay

5930

1066.27

3025

1051.45

2905

1081.69

 Married (y/n)

6877

0.697688

3522

0.698183

3355

0.697168

Birth order of the child

 Firstborn

6877

0.431002

3522

0.429869

3355

0.432191

 Secondborn

6877

0.320634

3522

0.327371

3355

0.313562

 Other

6877

0.248364

3522

0.24276

3355

0.254247

Projected number of children

 Ideal family size desired by the mother as a teen

6848

2.591268

3510

2.583191

3338

2.59976

Number of kids ever born

 Two children

6877

0.332994

3522

0.337876

3355

0.327869

 Three children

6877

0.300858

3522

0.30494

3355

0.296572

 Four children

6877

0.160535

3522

0.160136

3355

0.160954

 5+ children

6877

0.124618

3522

0.116695

3355

0.132936