The number of dairy cattle (including animals not in milk, and bulls for breeding) increased steadily in the early years of the 20th century as mechanisation and transport improved. Numbers remained relatively static from the depression years of the 1930s through the Second World War, until the mid-1970s. Between 1975 and 2005 increased fertiliser use, better pasture species, and expansion of dairying in the South Island all contributed to a steady increase in dairy cattle numbers. By 2005 dairying brought in about 20% of New Zealand’s total export earnings.