With increasing competition from trucks and automobiles in the 1920s, passenger volume began to decline along with less-than-carload freight, such as milk from the many dairy farms along the Ma and Pa's pastoral route. The Ma and Pa substituted more economical, self-propelled gas-electric passenger cars for steam-powered passenger trains in 1927–1928. Carload freight volume increased in the 1920s, however, as more industries located along the line, and earnings were strong enough for the company to declare dividends in 1930 and 1931. The Ma and Pa's relative prosperity ended with the economic downturn during the Great Depression, which cut the railroad's gross revenues by half from 1932 to 1935.