Even though the official poverty data are based on the 48 thresholds arranged by family size and number of children within the family, data users often want to get an idea of the "average" threshold for a given family size. The weighted average thresholds provide that summary. They are weighted averages because for any given family size, families with a certain number of children may be more or less common than families with a different number of children. In other words, among 3-person families, there are more families with two adults and one child than families with three adults. To get the weighted average threshold for families of a particular size, multiply each threshold by the number of families for whom that threshold applies; then add up those products, and divide by the total number of families who are of that family size.

For example, for 3-person families, 1999 weighted thresholds were calculated in the following way using information from the 2000 Current Population Survey:

Family type	Number of families	Threshold
No children (three adults)	5,213	*	$13,032	=	$67,935,816
One child (two adults)	8,208	*	$13,410	=	$110,069,280
Two children (one adult)	2,656	*	$13,423	=	$35,651,488
Totals	16,077				$213,656,584
Source: Current Population Survey, March 2000.

Dividing $213,656,584 by 16,077 (the total number of 3-person families) yields $13,290, the weighted average threshold for 3-person families. Please note that the thresholds are weighted not just by the number of poor families, but by all families for which the thresholds apply: the thresholds are used to determine which families are at or above poverty, as well as below poverty.

Poverty status was determined for all people except institutionalized people, people in military group quarters, people in college dormitories, and unrelated individuals under 15 years old. These groups also were excluded from the numerator and denominator when calculating poverty rates. They are considered neither "poor" nor "nonpoor."

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 level. These specified poverty levels are obtained by multiplying the official thresholds by the appropriate factor. For example, the average income cutoff at 125 percent of the poverty level was $21,286 ($17,029 x 1.25) in 1999 for family of four people.

Poverty Threshold in 1999, by Size of Family and Number of Related Children Under 18 Years Old (Dollars)
Size of family unit	Weighted average threshold	Related children under 18 years old
		None	One	Two	Three	Four	Five	Six	Seven	Eight or more
One person (unrelated individual)	8501
Under 65 years old	8667	8667
65 years old and over	7990	7990
Two people	10869
Householder under 65 years old	11214	11156	11483
Householder 65 years old and over	10075	10070	11440
Three people	13290	13032	13410	13423
Four people	17029	17184	17465	16895	16954
Five people	20127	20723	21024	20380	19882	19578
Six people	22727	23835	23930	23436	22964	22261	21845
Seven people	25912	27425	27596	27006	26595	25828	24934	23953
Eight people	28967	30673	30944	30387	29899	29206	28327	27412	27180
Nine people or more	34417	36897	37076	36583	36169	35489	34554	33708	33499	32208

Income deficit represents the difference between the total income 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.

Aggregate income deficit refers only to those families or unrelated individuals who are classified as below the poverty level. It is defined as the group (e.g., type of family) sum total of differences between the appropriate threshold and total family income or total personal income. Aggregate income deficit is subject to rounding, which means that all cells in a matrix are rounded to the nearest hundred dollars. (For more information, see "Aggregate" under "Derived Measures".)

Mean income deficit represents the amount obtained by dividing the total income deficit for a group below the poverty level by the number of families (or unrelated individuals) in that group. (The aggregate used to calculate mean income deficit is rounded. For more information, see "Aggregate income deficit.") As mentioned above, please use caution when comparing mean income deficits of families with different characteristics, as apparent differences may to some extent be a function of differences in family size. Mean income deficit is rounded to the nearest whole dollar. (For more information on means, see "Derived Measures".)

The poverty definition used in the 1980 census and later differed slightly from the one used in the 1970 census. Three technical modifications were made to the definition used in the 1970 census:

1. Beginning with the 1980 census, the Office of Management and Budget eliminated any distinction between thresholds for "families with a female householder with no husband present" and all other families. The new thresholds - which apply to all families regardless of the householder's sex - were a weighted average of the old thresholds.

2. The Office of Management and Budget eliminated any differences between farm families and nonfarm families, and farm and nonfarm unrelated individuals. In the 1970 census, the farm thresholds were 85 percent of those for nonfarm families; whereas, in 1980 and later, the same thresholds were applied to all families and unrelated individuals regardless of residence.

3. The thresholds by size of family were extended from seven or more people in 1970 to nine or more people in 1980 and later.

These changes resulted in a minimal increase in the number of poor at the national level. For a complete discussion of these modifications and their impact, see U.S. Census Bureau, Current Population Reports, " Characteristics of the Population Below the Poverty Level: 1980," P-60, No. 133.

With respect to poverty, the population covered in the 1970 census was almost the same as that covered in the 1980 census and later. The only difference was that in 1980 and after, unrelated individuals under 15 years old were excluded from the poverty universe, while in 1970, only those under age 14 were excluded. The limited poverty data from the 1960 census excluded all people in group quarters and included all unrelated individuals regardless of age. It was unlikely that these differences in population coverage would have had significant impact when comparing the poverty data for people since the 1960 census.

Because the questionnaires and data collection procedures differ, Census 2000 estimates of the number of people below the poverty level by various characteristics may differ from those reported in the March 2000 Current Population Survey. Please refer to www.census.gov/hhes/income/guidance.htmlfor more details.

Poverty status is not defined for households - only for families and unrelated individuals. Because some data users need poverty data at the household level, we have provided a few matrices that show tallies of households by the poverty status of the householder. In these matrices, the householder's poverty status is computed exactly the same way as described above. Therefore, to determine whether or not a "household" was in poverty, anyone who is not related to the householder is ignored.

Example #1: Household #1 has six members - a married couple, Alice and Albert, with their 10-year-old nephew, Aaron, and another married couple, Brian and Beatrice, with their 6-year-old son, Ben. Alice is the householder. Brian, Beatrice, and Ben are not related to Alice.

Household member	Relationship to Alice	Income
Alice	self (householder)	$5,000
Albert	spouse	$40,000
Aaron	related child	$0
Brian	unrelated individual	$0
Beatrice	unrelated individual	$5,000
Ben	unrelated individual	$0

The total income of Alice's family is $45,000, and their poverty threshold is $13,410, since there are three people in the family, with one member under age 18. Their income is greater than their threshold, so they are not classified as poor. Their ratio of income to poverty is 3.36 ($45,000 divided by $13,410). Alice's income-to-poverty ratio is also 3.36, because everyone in the same family has the same poverty status.
Even though Brian, Beatrice and Ben would be classified as poor if they lived in their own household, the household is not classified as poor because the householder, Alice, is not poor, as was shown in the computation above.

Example #2: Household #2 consists of four adults, Claude, Danielle, Emily, and Francis, who are unrelated to each other and are living as housemates. Claude, who is age 30, is the householder.

Household member	Relationship to Claude	Income
Claude	self (householder)	$4,500
Danielle	unrelated individual	$82,000
Emily	unrelated individual	$28,000
Francis	unrelated individual	$40,000

Because Claude is under age 65 and is not living with any family members, his poverty threshold is $8,667. Since his income, $4,500, is less than his threshold, he is considered poor. His ratio of income to poverty is 0.52 ($4,500 divided by $8,667).
Household #2 would be classified as poor because its householder, Claude, is poor, even though the other household members (who are not related to Claude) are not in poverty.