(FORTUNE Magazine) – The latest corporate tax bill--passed by Congress in early October and stuffed with $137 billion in tax breaks--will bring the business community's share of the national tax burden to its lowest level in decades. Economists Alan Auerbach and James Poterba have shown that most of the drop between 1960 and 1985 came from declining corporate profits rather than a falling tax rate. But over the past 15 years the effective federal tax rate for big corporations has dropped sharply, from 26.5% in 1988 to 17.2% in 2003, according to think tank Citizens for Tax Justice. Thanks to loopholes and avoidance schemes, an amazing 61% of U.S. corporations paid no taxes from 1996 to 2000, according to the Government Accountability Office. So who in the business world is paying? Berkshire Hathaway's $3.3 billion tax bill last year represented about 3% of the total income tax paid by all corporations. And next year, Warren Buffett says, he hopes to pay even more. He, for one, sees higher taxes as the byproduct of a worthy goal: higher profits. -- David Stires