The prediction about the future of the economy is based, as usual, on the amount of seasonal vomit found on the pavements in Westminster during the month of December up to Christmas eve. Perhaps surprisingly, this measure has proven to be a very reliable indicator of the size of the UK's gross domestic product (GDP) in the following year, as the graph shows.
Some economists have queried why there should be any relationship between sick and GDP. My answer is that the piles of vomit are a clear 'lead indicator', reflecting the underlying confidence of Londoners as they face the year ahead. When businesses provide generous Christmas parties at which the food and drink flows freely, we see the results on the pavement the next day. And when people are more confident, carefree and uninhibited, this is reflected in their drinking behaviour in pubs and clubs - with predictable (and measurable) results.