From the abstract:
Targeted ultra-high net worth wealth taxes can fund reductions in taxes on wages. Wealth taxes are harder to avoid than existing capital gains taxes and inheritance taxes, and can be more precisely targeted toward extreme wealth. Exit taxes to prevent capital flight are consistent with business law principles governing partnerships. Valuation disputes can be managed through existing property tax mechanisms and through private law provisions called “shotgun clauses.”
Most experts believe that wealth taxes are constitutional. The critical difference between wealth taxes and income taxes, the realization requirement, exists for administrative convenience, not as a constitutional requirement. Constitutional challenges can be discouraged by including in wealth tax legislation a savings clause that would create as a backup an economically equivalent income tax.