Well, the lower unemployment is the less corps
pay in taxes; to a floor of 5%. Jobs baby, jobs.
(Drill baby, drill).
Except getting those jobs requires corporate investment, which is less likely with higher tax rates. Your plan actually makes it more affordable to expand at a time when the economy needs it less, and makes economic expansion during times of severe unemployment less likely.
Simply put, lower taxes create jobs. Higher taxes cost jobs. Your plan raises taxes when jobs are scarce, resulting in not only less incentive to create jobs, but likely resulting in lay-offs because companies have to cut expenses to cover the increased taxes.