History

The days nobody is born

Every square is one date on the calendar, holding 21 years of American birth records. Weekends are stripped out first — hospitals schedule, so Tuesday is nothing like Sunday — and what's left is the date's own effect. Warm squares are busy days; cold squares are days the country declines to give birth. Tap or hover any square.

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Data & source

Source: US births by day, CDC/NCHS and SSA via FiveThirtyEight (CC BY 4.0), 1994–2014, fetched —. Each date's figure is its observed births divided by what its particular mix of weekdays predicts, so 1.00 is an ordinary day. Feb 29 is left out — it has a quarter of the evidence. Scheduled inductions and caesareans are what make the calendar visible at all: the pattern is about when doctors and parents choose, not when labour naturally starts.