<human>: Which is more popular: a yo-yo or a hula hoop?
<bot>: A yo-yo is more popular than a hula hoop. Yo-yos are the most popular toy in the world, with over 2 billion sold since the 1950s. Hula hoops were invented by a man named Richard Knerr in the 1930s and have been around ever since, but they're not nearly as popular.