Therefore, since the world population as of this writing is estimated at 7 billion you share your birthday with over 19 million people around the world (19,178,082).
Here are how many people you share your birthday with for countries around the world:
You currently share your birthday with about 859,178 people who reside in the United States. On a grand scale, you share your birthday with about 3.7 million Chinese and 3.2 million Indians. About 94,473 Canadians share a birthday as do 170,684 Brits and 445,126 Nigerians.
However, among the non-permanent residents of the world's least populated and smallest country in area, the Vatican City, you only share your birthday with 2 to 3 people on any given birthday. In the island country of Tuvalu, about 27 people sing "Happy Birthday" on any given day.
If you are lucky enough to have been born on February 29, you share your birthday with 1/1461 (because 366+365+365+365 equals 1461) of the population (0.068%) and so worldwide, you only share your birthday with a mere 4,791,239 people!