The Field Representative's Manual for 1968-1975 states that "White" includes Latin-Americans, unless they are definitely Black/Negro, Indian, or nonwhite. The "Other" category includes Japanese, Chinese, American Indian, Korean, Eskimo, and Hindu. Interviewers were instructed to "assume the race of all related persons is the same as that of the respondent," unless there was specific information to the contrary.

In 1968 and 1969, in cases in which the interviewer judged a person to have "mixed parentage," the instructions were to report the race of the nonwhite parent when the mixture was white and nonwhite. In the case of mixtures of nonwhite races, unless the "non-Negro race predominates" and "the person is regarded in the community as of the other nonwhite race," the interviewer was instructed to report the race of the person as "Negro." Beginning in 1970, the Field Representative's Manual instructed interviewers to report the race of the person's father for people uncertain how to respond.

Starting in 1970, interviewers were permitted to ask, "What is [person's] race?" in those cases where the interviewer's observation alone was not sufficient to determine the race.

For 1979-1991, the same categories were used as in 1978, except that 1978's "Alaskan Native or American Indian" was changed to 1979-1991's "Aleut, Alaskan Native, or American Indian," as defined by OMB Directive 15 (established in 1977). Throughout the period from 1978 to 1991, in cases where respondents chose some other racial category, they were asked to specify that other category, and were marked as "Another Group not Listed" by the interviewer.

For 1978--1981, the racial category of persons under age 17 was imputed, based on the interviewer's observation.

For example, 1978-1991's "Asian or Pacific Islander" category was replaced with "Chinese," "Filipino," "Hawaiian," "Korean," "Vietnamese," "Japanese," "Asian Indian," "Samoan," "Guamanian," and "Other Asian or Pacific Islander" for 1992-1995. Similarly, 1979-1991's "Aleut, Alaskan Native, or American Indian" became "Eskimo," "Aleut," and "American Indian" for 1992-1995. As in the pre-1992 period, those who chose some other category were asked to specify that category. Persons who self-identified as "Burmese, Fijian, Hmong, Indonesian, Loatian, Bangladeshi, Pakistani, Tongan, Thai, Cambodian, Sri Lankan, and so on," were coded into the "Other API" (Other Asian or Pacific Islander) category. Those who self-identified racial categories that could not be included in "Other Asian or Pacific Islander" (1992-1998), or "Other Asian" (1999 forward), were coded as "Other" in the NHIS public use files.

While the categories included on the survey form remained the same in the post-1995 period, the range of categories identified in the NHIS public use files shrank, due to confidentiality concerns. In addition, there was some fluctuation in the particular racial categories identified in the public use files for 1996 forward. "White," "Black/African American," "Chinese," "Filipino," and some category including "American Indian" were always identified. The category "Asian Indian" was included only in 1997 forward. Several categories with smaller population sizes that had been identified for 1992-1995 (such as "Hawaiian," "Korean," "Vietnamese," "Japanese," "Samoan," and "Guamanian") were subsumed into a general category such as "Other Asian or Pacific Islander" (for 1996-1998) or "Other Asian" (for 1999 forward).

Beginning in 1999, the "Other Asian or Pacific Islander" category became the more restricted "Other Asian" category. Regarding this change, the 1999 National Health Interview Survey (NHIS) Public Use Data Release: NHIS Survey Description, Appendix II ("Race and Hispanic Origin in the 1999 NHIS"), p. 69, states: "In compliance with the new race and ethnicity standards, the category 'Asian and Pacific Islander' is now split into two distinct categories, 'Asian' versus 'Native Hawaiian and Other Pacific Islander' (NHOPI), for data collection. Because confidentiality regulations on minimum sample size do not permit the NHIS to release data for Native Hawaiians and Other Pacific Islanders or some of the Asian subgroups separately, data are provided for the three largest Asian subpopulation groups, while the 'Other Asian' category combines groups that cannot be shown separately." Thus, the Pacific Islander groups, including Native Hawaiian and Samoan, amongst others, are included in the "Other Race" group.

Although "American Indian" is a category that occurs throughout the post-1977 period, the same is not true of "Alaskan Native"/"Eskimo" and "Aleut." In some years, the NHIS treated the category of "Alaskan Native"/"Eskimo" as distinct from "Aleut" (1979-1995). In one year, 1996, both categories were excluded, and people who self-identified as either were classified as "Other Race." From 1997-1998, the categories were subsumed under "American Indian." Finally, in 1999 forward, there was a general category, "American Indian, Alaska Native." This new general category is consistent with the 1997, revised OMB standards, in which the expression "Alaska Native" replaces the earlier "Alaskan Native," and is constituted by both Aleuts and Eskimos.

Given the suppression of particular racial categories in the post-1995 NHIS public use files for confidentiality reasons, users must interpret the term "Other" with particular care for this period. While, as noted above, in years prior to 1996, "Other" meant "another group not listed (on the original form)," beginning in 1996, the term has multiple meanings. In some cases for 1996-2002, it refers to self-selection of a racial category not on the flashcard presented to respondents (as was the case in earlier years). An example of this would be a respondent's self-reported racial identity as "Latino."

For 1996 forward, there are two other possible interpretations of "Other" in those cases where the term modifies some general category (i.e., 1996-1998's "Other Asian or Pacific Islander" and "Other Asian" for 1999 forward). First, "Other" sometimes refers to self-selection of a racial category which was not listed on the flashcard associated with the question, but which falls under a more general, general heading ("Asian or Pacific Islander" for 1996-1998, and "Other Asian" for 1999 forward). Second, "Other" sometimes refers to self-selection of a racial category listed on the flashcard (e.g., "Vietnamese"), which is suppressed for confidentiality reasons in the public release files, but which falls under the more general, geographic heading ("Asian or Pacific Islander" for 1996-1998, and "Other Asian" for 1999 forward).

Beginning in 2003, the "Other Race" category was dropped from the NHIS public use files, and a new category, "Primary Race Not Releasable," was added, to preserve the privacy of people whose racial category had very few members in the survey. As noted on the National Center for Health Statistic's Race and Hispanic Origin Information home page, beginning "with the 2003 NHIS, 'Other race' is no longer coded as a separate race response. Any responses that fall into this category are treated as missing, and the race is imputed if this is the only race response. In cases where 'Other race' is mentioned along with one or more OMB race groups, the 'Other race' response is dropped and the OMB race group information is retained."

In many cases, researchers need additional detail beyond that provided by the first digit. The categories sharing a common first digit of "3"--that is, those which fall under the general heading of "Aleut, Alaskan Native, or American Indian"--illustrate how the composite coding system works. Subcategories of "Aleut, Alaskan Native, or American Indian" available for only certain years share a common first digit of "3" but are distinguished by a second digit presenting detail or labels available only in some years (e.g., "31" for "Alaskan Native or American Indian," "32" for "Alaskan Native," "33" for "Aleut," and "34" for "American Indian").

Sometimes additional specificity is needed. This additional specificity is provided by the third digit. For example, the first digit "4" is used for any racial category falling under the general heading of "Asian or Pacific Islander." Since subgroups falling under this heading can be either "Asian" or "Pacific Islander," the second digit is used to indicate either "Asian" (a second digit of "1") or "Pacific Islander" (a second digit of "2"). The third digit distinguishes detail or labels available only in some years. For example, "400" refers to "Asian or Pacific Islander," "410" to "Asian," "411" to "Chinese," "420" to "Pacific Islander," and "421" to "Hawaiian."

As noted above, in cases where respondents chose some racial category not provided by the NHIS, they were asked to specify that other category and were marked as "Another Group not Listed" by the interviewer. Because the definition of "Other Race" varies across years, IPUMS NHIS composite codes use "500" as a general designation for "Other Race," and single, second digit increases in the 500s as specifications of different senses of "Other Race" (e.g., "510" for "Other Race (1968-1977)," "520" for "Other Race (1978)," and "530" for "Other Race (1979-1991)"). As discussed in detail in the previous section, the meaning of "Other" depends on which specific race groups are identified in a given year. Users should also keep in mind that in 1968-1977, "Other Race" is relative to interviewer-reported race, while in 1978 forward, it refers to self-selected race. Generally, users can treat "Other" categories with a common first digit of "5" as equivalent. The exception to this is the 1999-2003 period, where people who self-identify as "Pacific Islanders" are, in the NHIS public use files, categorized as either "Other Race" (1999-2002), or as "Primary Race Not Releasable" (2003 forward).

For 1997-1999, the single "Unknown" in the 1978-1996 NHIS public use files was subdivided into "Unknown-Refused," "Unknown-Not Ascertained," and "Unknown-Don't Know." "Unknown" in any form was dropped beginning in 2000. The reason for this, as noted in the National Center for Health Statistic's Race and Hispanic Origin Information home page, is that in "the 2000 survey year, the NHIS began implementation of hot-deck imputation of race and Hispanic origin, in order to improve the overall quality of the data. Similar to the editing procedures, the imputation procedures are based on methods developed by the U.S. Bureau of the Census. Race and Hispanic origin are first imputed from within a household, if available. If not, race and Hispanic origin are imputed between households which are matched by Hispanic origin within a small geographic area." Thus, starting in 2000, all persons in the IPUMS NHIS are a member of some racial category.