The little figures created by Danish toy company Lego are a rapidly exploding population – and according to XKCD will outnumber humans by 2019. Luckily they're only around 1/40th of the size of an adult human.
Lego began producing their iconic interlocking bricks in 1949, but the minfigures wouldn't appear until 1978. XKCD's Randall Munroe notes that Lego are already the world's largest manufacturers of tires.
Readers may also want to reflect on one of Munroe's older (but related) cartoons – on extrapolation.