POVIMPPOINT4 is a four digit variable with two implied decimal places for 2009, and a nine-digit variable with 3 implied decimal places for 2010 forward; the first 4 digits of the variable in 2010-forward are leading zeroes with 5 digits of meaningful data and 3 implied decimals.
These decimals are not placed in the syntax file users receive with their data extracts and must be generated by users within their statistical analysis package. Data users may use formatting functions to update these variables to reflect the correct decimals, or may divide POVIMPPOINT4 by 100 in 2009 and by 1000 in 2010-forward. Using these variables in their raw form directly from an IPUMS NHIS extract will result in values that are incorrect and not comparable across years.
POVIMPPOINT4 is a variable that includes imputed values to replace missing data for the original variable POVERTY, which reports the ratio of family income to the U.S. Census Bureau's poverty thresholds for the year in question (POVIMPPOINT4= INCIMPPOINT4/poverty threshold). Income to poverty threshold status was constructed based on income and the family's size and number of children.
The income-to-poverty ratios could not be calculated in two situations: 1) for families who did not supply adequate income information (i.e., those who would only indicate that their income was above or below $20,000 and those who declined to give any income information); and 2) for families where the number of children (persons under 18) equaled the number of family members (IPUMS NHIS code 98, indicating "indefinable"). In these cases, the ratio was imputed in POVIMPPOINT4. The complementary imputation flag variable IMPOVFLAG1 indicates whether responses in POVIMPPOINT4were reported or imputed.
Data users should see the Codes Tab for important information on transforming POVIMPPOINT4 for appropriate analysis.
Related Variables and Sources of Additional Information
POVIMPPOINT4 is the fourth of five variables that contain imputed values for the ratio of total family income to the poverty line. It was created as part of a set of variables that provide complete (i.e., without missing values) data on family income.
One of the purposes of NHIS data is to study relationships between income and health and to monitor health and health care for persons at different income levels. However, as the technical documentation on "Multiple Imputation of Family Income and Personal Earnings in the National Health Interview Survey: Methods and Examples" describes, non-response rates are high for questions on total family income in the previous calendar year and personal earnings from employment in the previous calendar year. For more information on the imputation methodology, see EMPSTATIMP1.
Before using the imputed income and earnings variables, researchers are strongly advised to read the NCHS documentation on imputed income, such as 2008 Imputed Family/Personal Earnings Files.
This documentation cautions that each of the five datasets must be merged with other data from the survey to form a single completed dataset. For IPUMS NHIS data users, the imputed income files have already been merged with other data from each survey year for 1997-2008, as part of the process of adding these imputed income files and variables to the IPUMS NHIS database.
The NCHS documentation for the imputed income files directs that analysis of the five versions of each imputed income variable should be done separately, using methods and software that are appropriate for such survey data (for example, SAS-callable SUDAAN or SAS-callable IVEware).
Only then can estimates and standard errors be combined using the combining rules described in the aforementioned document on "Multiple Imputation of Family Income and Personal Earnings in the National Health Interview Survey." The 2008 imputed income file documentation further warns:
Examples of correct data analyses and additional information about the procedures used to create the imputed data are provided in the technical documentation referred to above.
POVIMPPOINT4 is comparable for 2009 forward. For comparability over time, users should see the variables POVIMP1-POVIMP5 which provide income to poverty ratios in grouped intervals. These variables are less comparable over time due to changes in the response categories and methods used to probe for family income information.
- 2009-2017: All persons
- 2009-2017 : PERWEIGHT