The odds of being born in Japan
About 8.2 billion people live in the world today, and about 122.97 million of them live in Japan: roughly 1 in 67. Within Japan, nobody chooses the year, the prefecture or the household they are born into. Born in Japan is a life simulator that starts from that unchosen birth and lets you live a whole life, one year at a time.
Japan in the world
According to the United Nations' World Population Prospects 2024, the world population in 2024 was about 8.2 billion. According to Japan's 2025 Population Census, Japan's population on October 1, 2025 was 122.973 million, down 3.174 million from 2020. Dividing one by the other, about 1.5% of the world's people live in Japan, or roughly 1 in 67 (the two surveys refer to slightly different dates, so this is an estimate).
Within Japan, you are one of about 123 million people. The game uses statistics to decide which one you become.
Which prefecture
The game picks your birth prefecture in proportion to each prefecture's population (Statistics Bureau, Population Estimates). The chance of being born in Tokyo is about 11%, Kanagawa and Osaka about 7% each, and Tottori, the least populous, about 0.4%. Your prefecture shapes wages, schooling and the jobs you can choose. See Where and into what family you are born.
When, and into what household
You are born somewhere between 1947 and 2010, in proportion to the size of each generation. Born into the baby boom, you reach the bubble era in your prime; born into the employment ice age, you graduate into a year with few job openings. Your household's income decile and the chance of a single-parent home are also set from public statistics such as the Comprehensive Survey of Living Conditions.
An unchosen birth, a chosen life
You can't choose your birth, but you choose your schooling, work, marriage, housing and money at each turning point. You can replay the same birth to see how far your choices change a life. Special editions start you from a birth that leads toward a particular path: doctor, comedian, sumo wrestler, founder, prime minister and more.
Play Born in Japan (free, no sign-up) / All special editions
Sources
- World population (about 8.2 billion in 2024): United Nations, World Population Prospects 2024 https://population.un.org/wpp/
- Japan's population (122.973 million on October 1, 2025): Statistics Bureau of Japan, 2025 Population Census, Summary of Results PDF (Japanese)
- Population by prefecture: Statistics Bureau of Japan, Population Estimates (October 1, 2024)
"1 in 67" is an estimate from dividing the two population figures. Probabilities and events in the game also include game assumptions besides public statistics; each explainer page marks which is which. Related: Where and into what family you are born / How long you live