In determining the poverty status of families and unrelated individuals, the Census Bureau uses thresholds (income cutoffs) arranged in a two-dimensional matrix. The matrix consists of family size (from one person to nine or more people) cross-classified by presence and number of family members under 18 years old (from no children present to eight or more children present). Unrelated individuals and two-person families are further differentiated by age of reference person (RP) (under 65 years old and 65 years old and over).

To determine a person's poverty status, one compares the person's total family income in the last 12 months with the poverty threshold appropriate for that person's family size and composition (see example below). If the total income of that person's family is less than the threshold appropriate for that family, then the person is considered "below the poverty level," together with every member of his or her family. If a person is not living with anyone related by birth, marriage, or adoption, then the person's own income is compared with his or her poverty threshold. The total number of people "below the poverty level" is the sum of people in families and the number of unrelated individuals with incomes in the last 12 months below the poverty threshold.

Since ACS is a continuous survey, people respond throughout the year. Because the income questions specify a period covering the last 12 months, the appropriate poverty thresholds are determined by multiplying the base-year poverty thresholds (1982) by the average of the monthly inflation factors for the 12 months preceding the data collection. See the table in "Appendix A" titled "Poverty Thresholds in 1982, by Size of Family and Number of Related Children Under 18 Years (Dollars)," for appropriate base thresholds. See the table "The 2009 Poverty Factors" in "Appendix A" for the appropriate adjustment based on interview month.

For example, consider a family of three with one child under 18 years of age, interviewed in July 2009 and reporting a total family income of $14,000 for the last 12 months (July 2008 to June 2009). The base year (1982) threshold for such a family is $7,765, while the average of the 12 inflation factors is 2.22421. Multiplying $7,765 by 2.22421 determines the appropriate poverty threshold for this family type, which is $17,271. Comparing the familyincome of $14,000 with the poverty threshold shows that the family and all people in the family are considered to have been in poverty. The only difference for determining poverty status for unrelated individuals is that the person's individual total income is compared with the threshold rather than the family's income.

For various reasons, the official poverty definition does not satisfy all the needs of data users. Therefore, some of the data reflect the number of people below different percentages of the poverty thresholds. These specified poverty levels are obtained by multiplying the official thresholds by the appropriate factor. Using the previous example cited (a family of three with one related child under 18 years responding in July 2009), the dollar value of 125 percent of the poverty threshold was $ 21,589 ($ 17,271x 1.25). Income Deficit - Income deficit represents the difference between the total income in the last 12 months of families and unrelated individuals "below the poverty level" and their respective poverty thresholds. In computing the income deficit, families reporting a net income loss are assigned zero dollars and for such cases the deficit is equal to the poverty threshold. This measure provides an estimate of the amount, which would be required to raise the incomes of all poor families and unrelated individuals to their respective poverty thresholds. The income deficit is thus a measure of the degree of the impoverishment of a family or unrelated individual. However, please use caution when comparing the average deficits of families with different characteristics. Apparent differences in average income deficits may, to some extent, be a function of differences in family size.

Includes all people who have never been married, including people whose only marriage(s) was annulled.

Includes people ever married at the time of interview (including those "now married," "separated," "widowed," or "divorced").

Includes people whose current marriage has not ended through widowhood, divorce, or separation (regardless of previous marital history). The category may also include couples who live together or people in common-law marriages if they consider this category the most appropriate. In certain tabulations, currently married people are further classified as "spouse present" or "spouse absent." For federal definitions, "now married" does not include same-sex married people even if the marriage was performed in a state issuing marriage certificates for same-sex couples.

Includes people legally separated or otherwise absent from their spouse because of marital discord. Those without a final divorce decree are classified as "separated." This category also includes people who have been deserted or who have parted because they no longer want to live together but who have not obtained a divorce.

Includes widows and widowers who have not remarried.

Includes people who are legally divorced and who have not remarried. Those without a final divorce decree are classified as "separated." In selected tabulations, data for married and separated people are reorganized and combined with information on the presence of the spouse in the same household.

All people whose current marriage has not ended by widowhood or divorce. This category includes people defined above as "separated."

• Spouse Present - Married people whose wife or husband was reported as a member of the same household, including those whose spouses may have been temporarily absent for such reasons as travel or hospitalization.
• Spouse Absent - Married people whose wife or husband was not reported as a member of the same household or people reporting they were married and living in a group quarters facility.
• Separated - Defined above.
• Spouse Absent, Other - Married people whose wife or husband was not reported as a member of the same household, excluding separated. Included is any person whose spouse was employed and living away from home or in an institution or serving away from home in the Armed Forces.

Differences between the number of married males and the number of married females occur because: some husbands and wives have their usual residence in different areas; and husbands and wives do not have the same weights. By definition, the numbers would be the same.

The median age at first marriage is calculated indirectly by estimating the proportion of young people who will marry during their lifetime, calculating one-half of this proportion, and determining the age (at the time of the survey) of people at this half-way mark by osculatory interpolation. It does not represent the actual median age of the population who married during the calendar year. It is shown to the nearest tenth of a year. Henry S. Shryock and Jacob S. Siegel outline the osculatory procedure in Methods and Materials of Demography, First Edition (May 1973), Volume 1.

Beginning in 2008, people 15 years and over who were ever married ("married," "widowed," "separated," or "divorced") were asked if they had been married, widowed, or divorced in the past 12 months. They were asked how many times (once, two times, three or more times) they have been married, and the year of their last marriage.

The word "current" was dropped from the 1996-1998 question. Since 1999, the question states, "What is this person's marital status?" The American Community Survey began providing the median age at first marriage with the 2004 data. Data on marital history were first collected in 2008 at the request of the Department of Health and Human Services to provide more detailed annual information on the marital status of the population. Before 2008, the marital status question was asked of all people and only tabulated for those 15 and over. In 2008, marital status was moved from the basic demographic section, at the beginning of the ACS questionnaire, to the detailed person section - a part of the questionnaire where questions were asked of only people 15 and over. The marital history questions follow the marital status question on the questionnaire.

Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations have marital status distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the marital status distribution. This is particularly true for areas with a substantial GQ population.

The data on marital status can be compared to previous ACS years and to similar data collected on CPS and SIPP. Marital status is no longer asked on the Decennial Census. The marital history data, and particularly marriage and divorce rates derived from the questions asking if the person got married or divorced in the past 12 months is comparable to vital statistics collected by the National Center for Health Statistics (NCHS).