Identifying preferences inevitably invites controversy, because it requires a benchmark notion of an idealized tax system against which any deviations are deemed preferences. Perhaps not surprisingly, tax experts differ on what kind of system represents the ideal benchmark. The Treasury, for instance, uses a comprehensive, progressive income tax as its benchmark, with a few adjustments to reflect the practical realities of administering the ta system. Other analysts believe a broad-based consumption tax would be a better benchmark. In that case, several important preferences -- including accelerated depreciation, lower rates on capital gains and dividends, and some retirement provisions -- would be much smaller, or would not be identified as tax preferences at all. Meanwhile, other provisions, most notably companies' ability to deduct interest expenses, wolud be identified as preferences.