A version of this story appears in the September 2020 issue of National Geographic magazine. Philadelphia detected its first case of a deadly, fast-spreading strain of influenza on September 17, 1918.

Ask any parent, and they will tell you that having children is an expensive business. However, it turns out some mums and dads spend vast sums on items their kids don’t need or want. UK parents ...

Want more charts like these? See our charts on the secrets of the jobless recovery, the richest 1 percent of Americans, and how the superwealthy beat the IRS. How Rich Are the Superrich? A huge share ...