Footnotes for Historical Income Tables from the Current Population Survey (CPS), Annual Social and Economic Supplement (ASEC). To further protect respondent privacy, all estimates have undergone additional rounding. As a result, this year’s estimates may differ from previous publications and details may not sum to totals.

Please note that not all footnotes apply to all tables

N	Not available.
B	Base less than 75,000.
X	Not applicable.
Z	Zero or rounds to zero.
1/	Before 1983, based on CPI-U-X1
2/	Before 1967, CPI factors are extrapolated.
3/	Before 1967, data are for "Black and other races" combined
4/	People of Hispanic origin may be of any race.
5/	Data based on 1940 Census population controls.
6/	Implementation of expanded income questions to show wage and salary, farm self-employment, nonfarm self-employment, and all other non-earned income separately.
7/	Implementation of 1950 Census population controls.
8/	Implementation of first hotdeck procedure to impute missing income entries (all income data imputed if any missing). Introduction of 1960 Census-based sample design.
9/	Full implementation of 1960 Census sample design and population controls.
10/	Implementation of new procedures to impute missing data only.
11/	Questionnaire expanded to ask eight income questions.
12/	Implementation of a new CPS ASEC processing system.
13/	Introduction of 1970 Census-based sample design and population controls.
14/	Full implementation of 1970 Census-based sample design.
15/	Implementation of a new CPS ASEC processing system. Questionnaire expanded to ask 11 income questions.
16/	Some of these estimates were derived using Pareto interpolation and may differ from published data, which were derived using linear interpolation.
17/	First year medians were derived using both Pareto and linear interpolation. Before this year, all medians were derived using linear interpolation.
18/	Implementation of 1980 Census-based population controls. Questionnaire expanded to show 27 possible values from 51 possible sources of income.
19/	Implementation of Hispanic population weighting controls and introduction of 1980 Census-based sample design.
20/	Recording of amounts for earnings from longest job were increased to $299,999. Full implementation of 1980 Census-based sample design.
21/	Implementation of a new CPS ASEC processing system.
22/	Implementation of 1990 Census-based population controls.
23/	Data collection method changed from paper and pencil to computer-assisted interviewing. In addition, the 1994 CPS ASEC was revised to allow for the coding of different income amounts on selected questionnaire items. Limits either increased or decreased in the following categories: earnings limits increased to $999,999; Social Security limits increased to $49,999; Supplemental Security Income and public assistance limits increased to $24,999; veterans' benefits limits increased to $99,999; child support and alimony limits decreased to $49,999.
24/	Introduction of 1990 Census-based sample design.
25/	Full implementation of 1990 Census-based sample design and metropolitan definitions, 7,000 household sample reduction, and revised editing of responses on race.
26/	Starting in 1999, alternative income definition 7 includes federal EIC and EIC for the nine states that use federal eligibility rules to compute the state credit as a percentage of the federal EIC. The nine states are: Iowa, Kansas, Massachusetts, Maryland, New York, Oregon, Rhode Island, Vermont, and Wisconsin.
27/	Starting in 1999, 50th percentile is based on micro-sorted data.
28/	To adjust historical income estimates for inflation, the U.S. Census Bureau uses the Bureau of Labor Statistics’ (BLS) Chained Consumer Price Index for all Urban Consumers (C-CPI-U) between 2000 and 2022 and the Consumer Price Index for all Urban Consumers Retroactive Series (R-CPI-U-RS) between 1978 and 1999. For 1967 to 1977, the Census Bureau uses estimates provided by BLS from the CPI-U-X1 series. The CPI-U-X1 is an experimental series that preceded the CPI-U-RS and estimates the inflation rate in the CPI-U when applying the current rental equivalence method of measuring the cost of homeownership for years prior to 1983. The Census Bureau derived the R-CPI-U-RS for years before 1967 by applying the 1967 R-CPI-U-RS-to-CPI-U ratio to the 1947 to 1966 CPI-U.
29/	Implementation of 2000 Census-based population controls.
30/	Implementation of a 28,000-household sample expansion.
31/	Beginning with the 2003 CPS ASEC, respondents were allowed to choose one or more races. White alone refers to people who reported White and did not report any other race category. The use of this single-race population does not imply that it is the preferred method of presenting or analyzing data. The Census Bureau uses a variety of approaches.
32/	For the year 2001 and earlier, the CPS ASEC allowed respondents to report only one race group.
33/	Black alone refers to people who reported Black and did not report any other race category.
34/	Asian alone refers to people who reported Asian and did not report any other race category.
35/	Data have been revised to reflect a correction to the weights in the 2005 CPS ASEC.
36/	Beginning with 2009 income data, the Census Bureau expanded the upper income interval used to calculate medians and Gini indexes to $250,000 or more. Medians falling in the upper open-ended interval are plugged with "$250,000." Before 2009, the upper open-ended interval was $100,000 and a plug of "$100,000" was used.
37/	Implementation of 2010 Census-based population controls.
38/	The 2014 CPS ASEC included redesigned questions for income and health insurance coverage. All of the approximately 98,000 addresses were eligible to receive the redesigned set of health insurance coverage questions. The redesigned income questions were implemented to a subsample of the 98,000 addresses using a probability split panel design. Approximately 68,000 addresses were eligible to receive a set of income questions similar to those used in the 2013 CPS ASEC and the remaining 30,000 addresses were eligible to receive the redesigned income questions. The source of these 2013 estimates is the portion of the CPS ASEC sample that received the income questions consistent with the 2013 CPS ASEC, approximately 68,000 addresses.
39/	The source of these 2013 estimates is the portion of the CPS ASEC sample that received the redesigned income questions, approximately 30,000 addresses.
40/	Estimates reflect the implementation of an updated data processing system, allowing users to evaluate the impact, and should be used to make comparisons to 2018 and subsequent years.
41/	Implementation of 2020 Census-based population controls.

Page Last Revised - September 1, 2023

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