If ever there was a controversial icon from the statistics world, GDP is it. It measures income, but not equality, it measures growth, but not destruction, and it ignores values like social cohesion and the environment. Yet, governments, businesses and probably most people swear by it. According to François Lequiller, head of national accounts at the OECD, part of the problem is that perhaps we expect too much from this trusty, though misunderstood, indicator. But, the public is so used to GDP that we sometimes forget how hard it is to accurately sum all of the goods and services produced in a country together, from bricks and tableware to banking and software. First of all, to make such aggregating possible, you need to define what production is and what it is not. Our conventions may sometimes look arbitrary, such as when we exclude the output of domestic work that is carried out in the home. We do not consider, for example, that taking care of one’s own children is production, whereas we do when a hired nanny does the same work.