Shire horses are considered rare mainly due to the mechanization of agriculture and transportation during and after World War II, which drastically reduced the demand for draft horses and led to a severe population decline. By the 1950s and 1960s, numbers had dropped critically low, with fewer than 100 Shires at Britain's 1955 National Shire Horse Spring Show and only about 25 registered in the United States. Despite conservation efforts since the 1970s, they are still classified as an 'at-risk' breed, with fewer than 1,500 in the UK and less than 2,000 worldwide.