SOI Tax Stats - Estate Tax Study Data Sources and Limitations


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This page contains information about data sources and limitations for SOI's Estate tax study.

Please visit Estate Tax Statistics to access articles and tables from the study.

Analysts in the Estate Tax Section of SOI's Individual and Tax-Exempt Branch, collaborating with the SOI staff in the Kansas City Submission Processing Center, conduct the annual Estate Tax Study, which extracts demographic, financial, and bequest data from the United States Estate (and Generation-Skipping Transfer) Tax Return (Form 706), the Federal estate tax return. The study produces filing year data on estate taxation, focuses on a single-year of-death for a period of 3 years, and also provides periodic year-of-death estimates.

Year-of-death estimates are advantageous in that the included estates are therefore subject to the same tax law and similar economic conditions. A single year-of-death is sampled for 3 calendar years, and 99 percent of all returns for decedents who die in a given year are filed by the end of the second calendar year following the year-of-death. The Estate Tax Study for the period 2019–2021 concentrates on Year-of-Death 2019, the most recent year-of-death estimates available.

For each study year, 2019–2021, a sample was selected from the returns filed. The table below provides the number of returns sampled for each year-of-death, the total population estimates for those years, and the corresponding number of 2019 decedents.

Filing Year Returns Sampled Population Estimates 2019 Decedents
2019 4,452  6,409 178
2020 3,292  3,441 1,887
2021 5,582  6,158 3,197 
Total 13,326 16,008 5,314

Estate tax returns were sampled while the returns were being processed for administrative purposes, but before any audit examination. Returns were selected on a flow basis, using a stratified random probability sampling method, whereby the sample rates were preset based on the desired sample size and an estimate of the population. The design had three stratification variables: year-of-death, age at death, and size of total gross estate plus adjusted taxable gifts. For Filing Years 2019–2021, the year-of-death variable was separated into two categories: 2019 year-of-death and non-2019 year-of-death. Age was disaggregated into three categories: under 65, 65 under 80, and 80 and older (including age unknown). Total gross estate plus adjusted taxable gifts were limited to two categories: under $10.0 million, and $10.0 million or more. Sampling rates ranged from 0 percent to 100 percent; all returns under $10.0 million were not selected for the sample because they did not meet the Federal Estate Tax filing threshold. Returns which exceeded $10.0 million threshold were selected at the 100 percent rate.

Because almost 99 percent of all returns for decedents who die in a given year are filed by the end of the second calendar year following the year-of-death, and because the decedent's age at death and the length of time between the decedent's date of death and the filing of an estate tax return are related, it was possible to predict the percentage of unfiled returns within age strata. As a result, the sample weights were adjusted accordingly to account for returns for 2019 decedents not filed by the end of Filing Year 2021.