The other alternatives are attractive in theory but in practice are either impractical or offer only marginal improvements.
其他替代方案在理论上很有吸引力，但在实践中要么不切实际，要么只能提供微不足道的改进。
2
The most striking claim associated with the theory - that cuts in marginal rates could generate so much extra work effort that tax revenue would rise - is unlikely to apply except in extreme cases.