How is the height, weight and age of characters determined?

Question

While reading a wiki article about an anime character I found that they have mentioned every details of a character, including the details of his weight, height, age and even the date of birth.

How can you say that the anime character was born on a particular date and currently has a particular weight. What determines all these details. Are these details provided by the creator of the character?

Answer 1

They are provided by the creators, often together with artworks of the characters. Fans like them, so these infos can be used to advertise for the anime.

Here is an example (from Free!):