An operation which allows respondents to use the Census Bureau's Internet site to (1) ask questions and receive answers about the census form, job opportunities, or the purpose of the census and (2) provide responses to the short form.

Interpolation frequently is used in calculating medians or quartiles based on interval data and in approximating standard errors from tables. Linear interpolation is used to estimate values of a function between two known values. Pareto interpolation is an alternative to linear interpolation. In Pareto interpolation, the median is derived by interpolating between the logarithms of the upper and lower income limits of the median category. It is used by the Census Bureau in calculating median income within intervals wider than $2,500.

The data on veteran status were derived from answers to long-form questionnaire Item 20a. For census data products, a "civilian veteran" is a person 18 years old and over who, at the time of the enumeration, had served on active duty in the U.S. Army, Navy, Air Force, Marine Corps, or Coast Guard in the past (even for a short time), but was not then on active duty, or who had served in the Merchant Marine during World War II. People who had served in the National Guard or Military Reserves were classified as veterans only if they had ever been called or ordered to active duty, not counting the 4 to 6 months for initial training or yearly summer camps. All other civilians 18 years old and over were classified as nonveterans.

People who indicated in long-form questionnaire Item 20a that they had served on active duty in the past (civilian veterans) or were on active duty at the time of enumeration were asked to indicate in Question 20b the period or periods in which they served. People who served in both wartime and peacetime periods are tabulated according to their wartime service.

The responses to the question about period of service were edited for consistency and reasonableness. The edit eliminated inconsistencies between reported period(s) of service and the age of the person; it also removed reported combinations of periods containing unreasonable gaps (for example, it did not accept a response that indicated that the person had served in World War II and in the Vietnam era, but not in the Korean conflict).

People who indicated in long-form questionnaire Item 20a that they had served on active duty in the past (civilian veterans) or were on active duty at the time of enumeration were asked whether they had spent at least 2 years in total on active duty. The question asked for accumulated service (i.e., total service), which is not necessarily the same as continuous service. The years of military service question provides necessary information to estimate the number of veterans that are eligible to receive specific benefits.

There may be a tendency for the following kinds of people to report erroneously that they had served on active duty in the armed forces: (a) people who served in the National Guard or Military Reserves, but were never called to active duty; (b) civilian employees or volunteers for the USO, Red Cross, or the Department of Defense (or its predecessors, the Department of War and the Department of the Navy); and (c) employees of the Merchant Marine or Public Health Service. There is also the possibility that people may have misreported years of service in long-form questionnaire Item 20c because of rounding errors (for example, people with 1 year 8 months of active duty military service may have mistakenly reported "2 years or more").

Since census data on veterans are based on self-reported responses, they may differ from data from other sources, such as administrative records of the Department of Defense and/or the Department of Transportation. Census data also may differ from Department of Veterans Affairs data on the benefits-eligible population, since criteria for determining eligibility for veterans benefits differ from the rules for classifying veterans in the census.

The questions and concepts for veterans data for Census 2000 were essentially the same as those used for the 1990 census, with the following exceptions: (1) the period of military service categories were updated; (2) in an effort to reduce reporting error, the format of the years of military service question was changed from an open-ended one (how many years has...served?) to a closed-ended one (the respondent checked either of two boxes: less than 2 years/2 years or more); and (3) persons with service during World War II in the Womens Air Forces Service Pilots organization were first counted as veterans in Census 2000, a development that should not appreciably affect 1990-2000 comparability. Both the 2000 and 1990 veteran-status questions represented expanded versions of the corresponding question in the 1980 census, which asked only whether the person was a veteran or not. The expansion was intended to clarify the appropriate response for persons currently in the armed forces and for persons whose only military service was for training in the Reserves or National Guard.