As Treasury Secretary, Mellon focused on balancing the budget and paying off World War I debts in the midst of the Depression of 1920–21; he was largely unconcerned with international affairs and economic matters such as the unemployment rate. To Mellon's chagrin, his department was charged with enforcing Prohibition; he did not believe in teetotaling himself and viewed the law as unenforceable. Aside from balancing the budget, Mellon's top priority was an overhaul of the federal tax code. The income tax had become a major part of the federal government's revenue system with the passage of the Revenue Act of 1913, and federal taxation on income had increased during World War I to provide funding for the war effort. According to M. Susan Murnane, major reforms to the federal income tax in the aftermath of World War I were "inevitable", but the exact nature of the tax system in the 1920s was debated by conservatives and progressives within the Republican Party. Unlike the progressives in his party, Mellon rejected the redistributive nature of the taxation system that had been left in place by the Wilson administration. Owing in part to the high debts left over from the war, Mellon did not join with some conservatives in the party, who favored the virtual abolition of the income tax in favor of high tariff rates, excise taxes, a national sales tax, or some combination thereof.