How many people alive share your birthday?

Question

1. Roughly how many people alive today were born on the same day of the year as you (the same month and day, any year)? 2. Roughly how many were born on exactly the same date, including the year? State your assumptions.

Accepted Answer

About 22 million share your day of the year; about 300,000 to 400,000 share your exact birth date. Same day of the year. The world population is about 8 billion. Birthdays are close to evenly spread, so divide by 365: about 22 million people. (Birth rates vary a little by season and by day of the week, and 29 February has about a quarter of the usual number, but these are small corrections.) Same exact date. About 140 million babies are born each year worldwide, so about 380,000 per day. Not all survive to today: for someone born 30 years ago, roughly 90 to 95 per cent of that birth cohort is…

How many people alive share your birthday?

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