During the 20th century, there has been a shift away from rail and water transport in favour of road and air. The single most dramatic change has been the rise in personal mobility in developed countries, encouraged by cheap oil, affordable motor cars and lifestyles built around commuting, out-of-town shopping, dispersed families and leisure activities. Since World War II, the number of vehicles on the road has risen from about 40 million to some 680 million. The fastest growth is now found in the developing world, though car ownership is still low. There will be more than 1 000 million vehicles on the road by 2025.