Nearly 100% of the advertisers who made sponsorship deals in 1939 renewed their contracts for 1940; manufacturers of farm tractors made radios standard equipment on their machines;[63] wartime rationing of paper limited the size of newspapers and thus print advertisements, causing a shift toward radio sponsorship.[64] A 1942 act by Congress made advertising expenses a tax benefit,[64] which sent even automobile and tire manufacturers – who had no products to sell since they had been converted to war production – scurrying to sponsor symphony orchestras and serious drama on radio.[65] In 1940, only one-third of radio programs were sponsored, while two-thirds were sustaining; by the middle of the decade, the statistics had swapped.[66]