From the abstract:
Presidential candidates Elizabeth Warren and Bernie Sanders have both proposed ambitious new annual wealth taxes based on academic work by Emmanuel Saez and Gabriel Zucman. They project these proposals to raise trillions of dollars over the next ten years. Some critics challenge the Saez-Zucman approach to measuring the aggregate wealth of those subject to a wealth tax. Other critics including Larry Summers and Natasha Sarin have used data from estate tax returns and the relatively small amount of revenue the estate tax currently raises to question the revenue projections of these proposals. This comparison can be useful only if one thinks carefully about specific estate tax strategies and how these strategies translate to an annual wealth tax. This article engages in that exercise. When one takes a closer look at estate tax avoidance and how it maps onto an annual wealth tax, a much more complex narrative emerges.
That narrative has four major themes. First, there are some estate tax planning techniques (like valuation games and charitable contributions) which pose similar challenges to an annual wealth tax. These structures provide some support for critics like Summers and Sarin who argue that the annual wealth tax will struggle to raise the projected revenue. Second, other structures (such as grantor-retained annuity trusts ) work well to minimize estate taxes but are of limited use for structuring around an annual wealth tax. Projecting wealth tax revenue using estate tax revenue without considering the revenue consequences of these strategies will understate wealth tax revenue. Third, other techniques (including the use of lifetime estate/gift exemptions) highlight possible synergies between an estate and wealth tax. In many ways, a robust estate tax will make the wealth tax harder to avoid and vice-versa. The converse is also true: a poorly designed estate/gift tax will undermine an annual wealth tax. Adopting a wealth tax without strengthening the gift and estate makes little sense. Fourth, one of the major lessons of estate tax planning is that it is much easier to minimize estate taxes on future wealth than existing wealth. A myriad of techniques allow taxpayers to “freeze” the value of assets for estate tax purposes. Freezing techniques will also prove helpful in minimizing wealth taxes. It is possible that even a well-designed wealth tax will have a base that shrinks rather than grows over time.