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Summary statistics for the IBI analysis
| Income Group | Sample Size (N) | Mean IBI (months) | SE (months) | Modal IBI (months) |
|---|---|---|---|---|
| Middle-income | 29,016 | 30.5 | 18.5 | 24 |
| Low-income | 33,949 | 27.0 | 13.0 | 26 |
| Natural fertility | 276 | 34.9 | 19.7 | 24 |
| US WIC nonparticipant | 438,441 | 39.8 | 24.3 | 21 |
| US WIC participant | 331,128 | 41.5 | 26.8 | 21 |
Income groups classified by country GNI per capita: low-income = ≤ US $1085; middle-income = US $1086–13,205; high-income = ≥ US $13,205
