Yet behind the political noise, which escalated Thursday when Clinton detailed her proposal for the tax, its contribution to revenue has diminished over the years. As a result, any changes made to the policy are likely to have a minimal impact on tax receipts.
According to the IRS, the estate tax generated $16.4 billion in 2014, the latest year available. That's down roughly a third from 2006, when collections totaled $24.6 billion.
Receipts have fallen even more dramatically when looking farther back. In 1976, nearly 8 percent of all deaths resulted in an estate tax. In 2011, the latest year analyzed, that number was only 0.13 percent.
The estate tax now accounts for less than 1 percent of federal revenue, according to the nonpartisan Tax Foundation. That drop is surprising given the surging number of millionaires and billionaires over the past two decades, and the trillions of dollars supposedly being passed on to the next generation.
The main reason behind the decline is a higher number of exemptions. In 1976, estates had to pay a tax on a value of more than $60,000. Today, the threshold is $5.5 million for individual estates — meaning anyone who leaves their heirs less than that amount is excluded.
The top estate tax rate has also come down, from 70 percent in 1981, to 55 percent in 2000, to 40 percent today.
Another reason the estate tax is quietly dying is that the rich have become better at avoiding it. A vast array of trusts and estate-planning tools have made it easier for wealthy families to pass down assets without being subjected to the tax.
One popular tool they use is the grantor-retained annuity trust, which has helped several billionaires pass down assets free of gift or estate taxes.
"People utilize whatever legal machines they can use to move as much out of their estate as possible," said Roberton Williams, of the independent Tax Policy Center.
Trump has called for eliminating the tax.
Clinton's plan would presumably increase the revenues raised by the tax, by lifting the rate for higher brackets: She would impose a 50 percent rate on estates worth more than $10 million a person; a 55 percent rate on those over $50 million per person, and a 65 percent rate that would apply to individual estates over $500 million, or more than $1 billion for married couples.
Yet neither plan is likely to impact the wealthy or federal tax revenues, since so many of the highest payers are already working around the tax.
"At this point it's most symbolic," Williams said. "Twenty billion dollars is not chump change. But it doesn't really move the needle when it comes to the federal budget."
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