What is the fine-grained topic of the following text: Renown economist Laurence Kotlikoff believes that failure to enact the FairTax - choosing instead to try to "flatten" what he deems to be a non-flattenable income tax system - will eventuate into an irrevocable economic meltdown because of the hidden aspects of the current system that make political accountability impossible. Only return the topic.
Laurence Kotlikoff's belief in the potential economic meltdown due to failure to enact the FairTax