Are childhood obesity rates going down? Do 35 million birds die every year in the UK after hitting windows? How much money could the Chancellor find by changing the debt rule? And Professor Sir David Spiegelhalter contemplates the probability of his own conception.Tim Harford investigates some of the numbers in the news, and in life. Presenter: Tim Harford Reporter: Charlotte MacDonald Producers: Bethan Ashmead Latham, Natasha Fernandes and Nathan Gower Series producer: Tom Colls Production co-ordinator: Katie Morrison Sound mix: Neil Churchill Editor: Richard Vadon