In the last 20 or so years, there has been a major shift from a manufacturing to an information-based economy, with the closure of many factories (some of which had been in Slough for many decades). The factories are rapidly being replaced by office buildings. Hundreds of major companies have sited in Slough Trading Estate over the years, with its proximity to London Heathrow Airport and good motorway connections being attractive. In the 1960s, Gerry Anderson's film company was based in Slough, and his Supermarionation series, including "Thunderbirds", were filmed there.