During the early 20th century, improvements in regional transport infrastructure precipitated the decline of Salford's existing industries, including those at the Salford Docks. Increased foreign competition began to undermine the competitiveness of local textile processing businesses. Rising unemployment during the Great Depression of the 1920s and 1930s, and a significant economic decline in the decades following the Second World War contributed toward a fall in Salford's population. By 1939 local coal mining had almost stopped, and cotton spinning had by 1971 ceased completely. Between 1921 and 1939, the population of Salford decreased by 29%, from 234,045 to 166,386, far greater than the rate of decline within the whole of North West England.