Indeed, the ultra-wealthy pay far less than 40% effective estate tax. Seems closer to 15% due to creative accounting, which is further reduced to 6.8% by charitable contributions:
> Specifically, for single decedents, estate taxes paid equal 6.8% of the value of Forbes wealth at death. The value of their gross estate is 39% of the Forbes estimate of their wealth. This large gap, already noted in earlier work (Raub et al., 2010), is likely to reflect the various techniques available to high-net-worth individuals to undervalue assets in the context of the estate tax. Taxable estate is then 45% of gross estate (due to deductions primarily gifts to charities) and on that base the tax rate is 39% (Balkir et al., 2025, Table 4 Panel B).
https://www.nber.org/system/files/working_papers/w34170/w341...
