Ina room of 23 random peoplethe probability of two of them sharing a birthday is 50 percent. Increase the number of people to just 70 and the probability is 99.9 per cent.
The probability reaches 100% when the number of people reaches 366.
I didn’t make it that’s just what it’s called.
I guess the paradox is you would expect it to be more linear and not to hit the 99 per cent with such a small number of people as 70.