Cribsheet Summary

The first week with a baby can make a normal adult treat a burp cloth like a legal document.

Emily Oster, an economist at Brown University, writes from inside that fog with a ruler in one hand and a raised eyebrow in the other. After applying data to pregnancy in Expecting Better, she turns to the baby years in Cribsheet: feeding, sleep, childcare, screens, discipline, and the thousand small verdicts that arrive before breakfast.

Her concrete claim is simple and useful: many parenting rules are weak evidence wearing a judge's robe. Better data can tell you which risks are real, which benefits are overstated, and where your own family values must do the deciding.

The book's nursery has a scale in it, but the scale does not weigh good mothers and bad fathers. It weighs claims.

In a hospital room, advice arrives faster than discharge paperwork. One nurse says wake the baby to feed. Another says never wake a sleeping baby. A relative has a story, a forum has a war, and someone on the internet has discovered capital letters.

Oster's great service is to ask what kind of evidence is sitting on the scale. A study that finds breastfed children do better in school may be true as far as it goes. The trouble is that breastfed children often differ from formula-fed children in many other ways. Their parents may have more money, more leave from work, more education, or more help at home. That makes the comparison dirty.

A correlation is a rumor with a spreadsheet.

This is why Oster keeps returning to better tools. Randomized trials can separate cause from background noise, because people are assigned to groups by chance. Sibling comparisons can help too, because one child in the same family may be breastfed longer than another. These tools are not magic, but they are better than asking panic to grade its own homework.

The caution matters beyond parenting. Modern life sells certainty by the pound. Food rules, work habits, school choices, and health scares all use the same trick: they point to a pattern and call it proof.

Andrew Wakefield's 1998 paper linking the MMR vaccine to autism became a famous warning about that trick. The claim collapsed, but the fear had already learned to walk.

Oster is not telling parents to ignore experts. She is telling them to notice when expert-sounding advice has skipped the hard part.