The First World War: Revenue Act of 1916, 630; Revenue Acts of 1918 and 1921, 631; criteria used by the Government, 632; extent of amortization under this law, 634; the question of incentives, 634. — The Second World War: Second Revenue Act of 1940, 636; administration of this law, 637; changes in the law in 1942, 639. — Accelerated depreciation as an incentive to plant expansion, 641. — Conclusions, 645.