Although 23 people yields a 50% probability, increasing the group size to just 70 people pushes the chance of a shared birthday to 99.9%.

Instead of comparing one person to the rest of the group, every individual is compared to each other, creating 253 unique pairings among 23 people.

Our brains tend to linearly assume we need around 183 people to reach a 50% chance, making the mathematically sound answer feel completely absurd.

This principle dictates that if you distribute 367 people across 366 possible dates, including leap years, at least one date must contain two people.