The variables needed to calculate demographic survey and decennial census response rates are based on classifications suggested by the American Association for Public Opinion Research (AAPOR), 2008. This effort helps to ensure consistency to external standards while allowing the Census Bureau to adapt the classification to our specific circumstances.

The terms and variables are partitioned into three sections. The first section describes eligibility status. Variables in this section distinguish among sample units that are known to be eligible for data collection, are known to be ineligible for data collection, or have an unknown eligibility for data collection. The data collection target population guides the distinction between eligible and ineligible units. The second section describes the response status for eligible sample units. The third section provides detail on nonrespondents by identifying the type of (or the reason for) the nonresponse.

1.1 Eligibility Status

The total number of units selected for a sample is defined as n. These units can be classified by their eligibility status: eligible for data collection (E), ineligible for data collection (I), or of unknown eligibility (U). The target population determines the classification of a unit as eligible or ineligible. The target population refers to persons, households, or other units upon which inferences (estimates) are made. Specific units may be considered eligible for one census or survey but ineligible for another, depending upon the target population. For example, in a survey of housing, vacant units may be part of the target population, but these same vacant units may be outside the target population in an income survey and would therefore be classified as ineligible.

Variable	pi (Probability of selection)
Definition	Probability of selecting a unit for the sample, including all subsampling, even subsampling for nonresponse follow-up.
Variable	wii (Sample weight)
Definition	The inverse of the final probability of selecting a unit for the sample, including all subsampling, such as subsampling for nonresponse follow-up.
Term	E (Eligible)
Definition	The weighted count of sample units that are eligible for data collection. A person, household, or other unit is eligible if an attempt has been made to collect data and the unit is confirmed to be a member of the target population. Both occupied and vacant units can be considered eligible.
Variable	ei – An indicator variable for whether a unit selected for the sample is eligible for data collection. If a sample unit is eligible, ei = 1, else ei = 0.
Computation	Sum of the sample weight for all eligible units.
Reference	Equivalent to the sum of AAPOR "Interview" disposition code (1.0) and “Eligible, non-interview” disposition code (2.0).
Term	I (Ineligible)
Definition	The weighted count of sample units that are ineligible for data collection. This is the number of units for which an attempt has been made to collect data and it is confirmed that the unit is not a member of the target population.
Variable	ii – An indicator variable for whether a unit selected for the sample is confirmed as not being a member of the target population at the time of data collection. Information confirming ineligibility may come from observation, from a respondent, or from another source. Some examples of ineligible units include: demolished structure, entire household in armed forces, unit under construction, unit screened out, nonresidential unit, fax/data line or disconnected number (in random-digit dial surveys), and vacant unit. If a sample unit is ineligible, ii = 1, else ii = 0.
Computation	Sum of the sample weight for all ineligible units.
Reference	Equivalent to AAPOR “Not Eligible” disposition code (4.0).
Term	U (Unknown eligible)
Definition	weighted count of sample units for which eligibility is unknown.
Variable	ui – An indicator variable for whether the eligibility of a unit selected for the sample could not be determined. This occurs if data are not collected from a unit and there is no information available about whether or not the unit is a member of the target population. Some examples of units with unknown eligibility include: unable to locate unit, unable to reach/unsafe area, address never assigned/worked, or number always busy or call screening/blocking (in random digit dial surveys). If a sample unit is of unknown eligibility, ui = 1, else ui = 0.
Computation	Sum of the sample weight for all units with an unknown eligibility.
Note	Surveys that have large number of units with unknown eligibility (e.g., random-digit-dial surveys) may estimate the proportion of cases of unknown eligibility that are eligible, ee. This estimated proportion may be used to adjust the estimates of I and E. The survey must have a defensible basis for estimating ee (e.g., assume that the ratio of eligible to not eligible cases among the known cases applies to the unknown cases). Without a defensible basis, ee may not be used to adjust the estimates of I and E. The number of eligible units may be adjusted by adding (ee * U) to E. The number of ineligible units may be adjusted by adding (U ‑ (ee * U)) to I. The basis for estimating ee must be stated explicitly and the justification described clearly.
Reference	Equivalent to AAPOR “Unknown Eligibility, Non-Interview” disposition code (3.0).
Term	T (Total count)
Definition	The weighted count of all units (eligible, ineligible, and of unknown eligibility) selected for the sample.
Computation	Sum of the sample weights for the eligibility status outcome of all units.
The relationship between E, I, U, and T is T = E + I + U. For the ith unit ei + ii + ui = 1.

1.2 Response Status

Response status is determined only for eligible sample units. The definition of sufficient data for a unit to be classified as a response will vary across surveys and will impact the count of responding units.

Term	R (Response)
Definition	The weighted count of eligible sample units with sufficient data to be classified as a response. In a multi-mode survey or census, responses may be obtained by mail, Internet, telephone, fax, touch-tone data entry/voice recognition, or personal visit.
Variable	ri – An indicator variable for whether an eligible unit selected for the sample responded to the survey and provided sufficient data. If a unit responded, ri = 1 else ri = 0 (note ri = 0 for units classified as U or I and units that did not respond with sufficient data).
Computation	Sum of the sample weights for all response outcomes.
Reference	Equivalent to AAPOR I+P (complete interviews + partial interviews) disposition codes (1.1) and (1.2).

1.3 Reasons for Nonresponse

To improve interpretation of the response rate and better manage resources, it is recommended that whenever possible, reasons for (or types of) nonresponse be measured. Six specific terms describing nonresponse reasons are defined below. These terms (REF, NOH, TA, LB, INSF, and OTH) define specific nonresponse reasons for sample units.

Term	REF (Refusal)
Definition	The weighted count of eligible sample units that refused to respond to the survey.
Variable	refi – An indicator variable for whether an eligible sample unit refused to respond to the survey. If a unit refused to respond, refi = 1, else refi= 0.
Computation	Sum of the sample weights for all “refusal” outcomes.
Reference	Equivalent to AAPOR “R” (refusal and break-off) – disposition code (2.10).
Term	NOH (No one home)
Definition	The weighted count of eligible sample units that did not respond because no one was found at home during the interviewing period.
Variable	nohi – An indicator variable for whether an eligible sample unit did not respond to the survey because no one was found at home during the interviewing period. If a unit was “no one home,” nohi = 1, else nohi = 0.
Computation	Sum of the sample weights for all “no one home” outcomes.
Reference	Equivalent to AAPOR “No one at residence” – disposition code (2.24).
Term	TA (Temporarily absent)
Definition	The weighted count of eligible sample units that did not respond because the occupants were temporarily absent during the interviewing period.
Variable	tai – An indicator variable for whether an eligible sample unit did not respond to the survey because the occupants were temporarily absent during the interviewing period. If a unit was “temporarily absent,” tai = 1, else tai = 0.
Computation	Sum of the sample weights for all “temporarily absent” outcomes.
Reference	Equivalent to AAPOR “Respondent away/unavailable” – disposition code (2.25).
Term	LB (Language barrier)
Definition	The weighted count of eligible sample units that did not respond because an interviewer or interpreter was not available to conduct the interview in the required language.
Variable	lbi – An indicator variable for whether an eligible sample unit selected for the sample did not respond to the survey because an interviewer or interpreter was not available to conduct the interview in the required language. If a unit did not respond due to a language barrier, lbi = 1, else lbi = 0.
Computation	Sum of the sample weights for all “language barrier” outcomes.
Reference	Equivalent to AAPOR “Language” – disposition code (2.33).
Term	INSF (Insufficient data)
Definition	The weighted count of eligible sample units selected for the sample that participated but did not provide sufficient data to qualify as a response.
Variable	insfi - An indicator variable for whether an eligible sample unit that was selected for the sample returned a questionnaire, but did not provide sufficient data to qualify as a response. If a unit returned a questionnaire but fails to provide sufficient data to qualify as a response, insfi = 1, else insfi = 0.
Computation	Sum of the sample weights for “insufficient data” outcomes.
Reference	Equivalent to AAPOR “Break off” and “Break-off questionnaire too incomplete to process” – disposition code (2.12).
Term	OTH (Other nonresponse)
Definition	The weighted count of sample units that did not respond for a reason other than refusal, no one home, language barrier, temporarily absent, insufficient data, or if a unit was classified as unknown eligibility.
Variable	othi – An indicator variable for whether a unit selected for the sample was a nonresponse for a reason other than refusal, no one home, language barrier, temporarily absent, or insufficient data or if the unit was classified as unknown eligibility. If a unit does not respond for reasons other than refusal, no one home, language barrier, temporarily absent, insufficient data, or if a unit was classified as unknown eligibility, othi = 1, else othi = 0.
Computation	Sum of the sample weights for “other nonresponse” outcomes.
Reference	Equivalent to AAPOR “Other,” “Dead,” “Physically or mentally unable,” and “Miscellaneous” – disposition codes (2.30), (2.31), (2.32), and (2.35).

2.1 Primary Response Rates

Rate	UR rate (Unit Response Rate)
Definition	The ratio of responding units to the sum of eligible units and units of unknown eligibility (expressed as a percentage).
Computation	UR rate = [R/(E+U)] * 100
Reference	Equivalent to AAPOR Response Rate 2 (RR2).
Rate	AR rate (Alternative Response Rate)
Definition	The ratio of responding units to estimated eligible units (expressed as a percentage).
Computation	AR rate = [R/[(E)+ee*U] * 100 where: ee = estimated proportion of cases of unknown eligibility that are actually eligible. The survey must have a defensible basis for estimating ee. If such a basis does not exist, then ee may not be used to adjust the estimates of I and E and the survey may not estimate the AR rate.
Reference	Equivalent to AAPOR Response Rate 3 (RR3).
Rate	URM rate (Cumulative Unit Response Rate for multistage surveys)
Definition	The product of unit response rates for all stages of the survey
Computation	URM rate = where, URj is the unit response rate at stage j of the survey and k is the total number of stages. If another equation yields a more accurate estimate of the cumulative unit response rate because it uses additional information about the frame, then that equation should be used. If the cumulative response rate is misleading or inaccurate, an explanation of the problems must be documented.

2.2 Detailed Eligibility and Nonresponse Rates

3.1 Item Response Rates

Term	IREQA (Weighted total of responses required for data item A)
Definition	The weighted count of sample units for which a response to item A is required. A response is required for item A unless it is a valid skip item.
Variable	ireqAi – An indicator variable for whether a response to item A is required. If a response is required, ireqAi = 1, else ireqAi = 0
Computation	Sum of the sample weight for all units requiring a response to item A.
Term	ITEMA (Total valid responses for data item A)
Definition	The weighted count of sample units for which a valid response to item A is obtained.
Variable	itemAi – An indicator variable for whether a valid response to item A is obtained. If a valid response is obtained, itemAi = 1, else itemAi = 0
Computation	Sum of the sample weight for all units requiring a response to item A for which a valid response is obtained.
Rate	IRA rate (Item response rate for data item A)
Definition	The ratio of the weighted count of units with a valid response to item A to the weighted count of units that required a response to item A.
Computation	IRA rate = ITEMA / IREQA
Rate	TIRA rate (Total item response rate for data item A)
Definition	The product of the weighted item response rate for item A and either the unit response rate, reflecting the response rate to item A after accounting for both unit nonresponse and item nonresponse, or the cumulative unit response rate for multistage surveys.
Computation	TIRA rate = IRA * UR or TIRAM rate = IRA * URM

3.2 Item Allocation Rates

Item nonresponse is measured through the calculation of allocation rates. Allocation involves using statistical procedures, such as within-household or nearest neighbor matrices populated by donors, to impute for missing values.

Term	ALLOA (Total number of responses allocated for item A)
Definition	The weighted count of sample units for which a response is allocated to item A.
Variable	alloAi – An indicator variable for whether a response is allocated to item A. If a response is obtained, alloAi = 1, else alloAi = 0
Computation	Sum of the sample weight for all units requiring a response to item A for which a response is allocated.
Rate	IAA rate (Item allocation rate for data item A)
Definition	The ratio of the weighted count of units with an allocated response to item A to the weighted count of units that required a response to item A.
Computation	IAA rate = ALLOA / IREQA = 1 - IRA rate

The American Association for Public Opinion Research. 2008. Standard Definitions: Final Dispositions of Case Codes and Outcome Rates for Surveys. 5th edition. Lenexa, Kansas: AAPOR.