Assigning Sampling weights in case of Multi stage sampling

A multi-stage stratified cluster design greatly enhances the feasibility of data collection, it results in differential probabilities of selection; consequently, each sampling unit or in the assessment does not necessarily represent the same number of students in the population, as would be the case if a simple random sampling approach were employed.

To account for differential probabilities of selection due to the nature of the design and
to ensure accurate survey estimates, Sampling weights are needed to correct for imperfections in the sample that might lead to bias and other departures between the sample and the reference population. Such imperfections include the selection of units with unequal probabilities, non-coverage of the population, and non-response.

In other words, the purposes of weighting are:
• To compensate for unequal probabilities of selection.
• To compensate for (unit) non-response/ and or non-coverage.
• To adjust the weighted sample distribution for key variables of interest and to make it conform to a known population distribution.

So, usually three types of weights are assigned:

• Sampling weight to account for unequal probability of selection
• Weights for non response
• Post stratification weights

Though in majority of the cases only sampling weights and weights for non-coverage/non-response is used.

Calculation of sampling weights

Calculation of sampling weights usually starts with the construction of the base weight for each sampled unit, to correct for their unequal probabilities of selection. In general, the base weight of a sampled unit is the reciprocal of its probability of selection into the sample.

For multi-stage designs, the base weights must reflect the probabilities of selection at
each stage and the overall base weight the household is obtained as before, by taking the reciprocal of its overall probability of selection.

The adjustment of sample weights for non-response/non-coverage

It is rarely that all desired information is obtained from all sampled units in surveys. For instance, some households may provide no data at all while other households may provide only partial data. Further not all sampling units in samples may be covered.

Revealing Truth Behind Poverty and Poverty line

The most commonly used way to measure poverty is based on incomes or consumption levels. A person is considered poor if his or her consumption or income level falls below some minimum level necessary to meet basic needs, which is usually defined as the "poverty line". Information on consumption and income is obtained through sample surveys, during which households are asked to answer detailed questions on their spending habits and sources of income. But the contentious issues are encapsulated in definition as what is necessary to satisfy basic needs varies across time and societies.

 Globally

It is preemptive that while measuring poverty world-wide, the same reference poverty line has to be used, and expressed in a common unit across countries. Thus World Bank uses reference lines set at $1 and $2 per day in 1993 Purchasing Power Parity (PPP) terms (where PPPs measure the relative purchasing power of currencies across countries)

Empirical Framework: Poverty in India

The first absolute definition of poverty was given by Dandekar-Rath, who defined it as an expenditure of Rs 15 per capita per month for the Indian rural population at 1960-61 prices, and Rs 18 per capita per month for the urban population. The Government of India set up an Expert Group to suggest a methodology to measure poverty. The group submitted its report in 1993 and suggested a new poverty line: Rs 49 and Rs 56, for rural and urban areas at 1973-74 prices. This line was higher in real terms by approximately 15 per cent.
The most widely used measure of poverty in India is the 'head-count ratio'. The head-count ratio is computed on the basis of NSS data on consumption expenditure. People with an income below the poverty line are 'poor' and the proportion of the poor to the aggregate population is the head-count ratio. In the early-'60s, the GOI appointed a special working group of eminent economists to assess the level of poverty in India. The experts came up with a definition of the Poverty Line. This was based on a nationally desirable minimum level of consumption expenditure based on a standard balanced diet prescribed by the Nutrition Advisory Committee.

In India, poverty is officially linked to a nutritional baseline measured in calories (food energy method). The Planning Commission defines poverty lines as a per capita monthly expenditure of Rs 49 for the rural areas and Rs 57 in urban areas at 1973-74 all India prices. These poverty lines correspond to a total household per capita expenditure sufficient to provide, in addition to basic non-food items – clothing, transport – a daily intake of 2,400 calories per person in rural areas and 2,100 in urban areas. Individuals who do not meet these calorie norms fall below the poverty line.

In other words, any family who could not afford to buy a rudimentary food basket, which when consumed yielded a minimum level of calories, was considered poor.

For decades, the Planning Commission of the Government of India has regularly published “official” headcount poverty ratios, separately for rural and urban areas of every Indian state and Union Territory. The poverty counts are computed as the fraction of the population living in households with consumption per head below a poverty line. The poverty lines have been calculated to represent the minimum monthly expenditure per head associated, on average, with a sector-specific minimum calorie intake, recommended by the Indian National Institute of Nutrition. The lines are kept constant in real terms, and are inflated by using two different state-specific price indexes: the Consumer Price Index for Agricultural Labourers (CPIAL) for rural areas, and the Consumer Price Index for Industrial Workers (CPIIW) for the urban sector.

Expenditure data are collected by the Indian National Sample Survey Organization (NSSO) approximately every five years, from a large sample of Indian households interviewed over a one-year period.

Until the 50th round, carried out in 1993-94, all NSS surveys adopted a 30-day recall period for all expenditure items. This choice of recall period is unusual, as most statistical agencies use a shorter reporting period for items that are typically purchased frequently, like food, and a longer period for infrequent expenditures like clothing, footwear, educational expenses, and durables. Several experimental studies find that expenditure reports for frequently purchased items are on average proportionally lower when the recall period becomes longer.


Poverty status in India

Despite splendid achievements, India is still among the poorest nations in the world in per capita terms. It has managed to reduced poverty over that period, but only since about 1975 has the decline becomes fairly steady, albeit slow. And, although the incidence of poverty has declined from 45 to 36 percent between 1950 to 1993-94, population growth caused the number to ballooned up to double in the same period from 164 to 320 million. Of that total three out of four (76 percent) live in rural area.

The NSS 55th round in 2000 indicates that for the year 1999-2000, 23.10 per cent of the people are below the poverty line In absolute numbers it is 2,602,500,000 people. 23.62 per cent i.e. 670.07 lakh persons are urban poor and 27.09 per cent, i.e. 1932.43 lakh persons are rural poor (Government of India, Press Information Bureau). Almost 30 per cent of the population still lives below the poverty line of less than 100 US$ per capita annually (Sengupta, 1992).

In India there are so many people close to the poverty line, the simple headcount ratio, which gets almost all the attention, is extremely sensitive to small changes in both reality and measurement error. Further it would be gross generalization to assume all people living below poverty line are alike.

Indian poverty lines are also differentiated geographically, by state, and by urban and rural households within each state. Thus it is important to point that there is nothing like all India poverty line, either for urban or rural, instead, poverty counts are made for each state, within each sector, and added up to get urban and rural totals. Thus it is imperative to assess poverty at regional level, state level to understand the disparities and analyze who are these poor people and why they are still poor even after more than fifty years of independence.



The most commonly used way to measure poverty is based on incomes or consumption levels. A person is considered poor if his or her consumption or income level falls below some minimum level necessary to meet basic needs, which is usually defined as the "poverty line". Information on consumption and income is obtained through sample surveys, during which households are asked to answer detailed questions on their spending habits and sources of income. But the contentious issues are encapsulated in definition as what is necessary to satisfy basic needs varies across time and societies.

 Globally

It is preemptive that while measuring poverty world-wide, the same reference poverty line has to be used, and expressed in a common unit across countries. Thus World Bank uses reference lines set at $1 and $2 per day in 1993 Purchasing Power Parity (PPP) terms (where PPPs measure the relative purchasing power of currencies across countries)

Empirical Framework: Poverty in India

The first absolute definition of poverty was given by Dandekar-Rath, who defined it as an expenditure of Rs 15 per capita per month for the Indian rural population at 1960-61 prices, and Rs 18 per capita per month for the urban population. The Government of India set up an Expert Group to suggest a methodology to measure poverty. The group submitted its report in 1993 and suggested a new poverty line: Rs 49 and Rs 56, for rural and urban areas at 1973-74 prices. This line was higher in real terms by approximately 15 per cent.
The most widely used measure of poverty in India is the 'head-count ratio'. The head-count ratio is computed on the basis of NSS data on consumption expenditure. People with an income below the poverty line are 'poor' and the proportion of the poor to the aggregate population is the head-count ratio. In the early-'60s, the GOI appointed a special working group of eminent economists to assess the level of poverty in India. The experts came up with a definition of the Poverty Line. This was based on a nationally desirable minimum level of consumption expenditure based on a standard balanced diet prescribed by the Nutrition Advisory Committee.

In India, poverty is officially linked to a nutritional baseline measured in calories (food energy method). The Planning Commission defines poverty lines as a per capita monthly expenditure of Rs 49 for the rural areas and Rs 57 in urban areas at 1973-74 all India prices. These poverty lines correspond to a total household per capita expenditure sufficient to provide, in addition to basic non-food items – clothing, transport – a daily intake of 2,400 calories per person in rural areas and 2,100 in urban areas. Individuals who do not meet these calorie norms fall below the poverty line.

In other words, any family who could not afford to buy a rudimentary food basket, which when consumed yielded a minimum level of calories, was considered poor.

For decades, the Planning Commission of the Government of India has regularly published “official” headcount poverty ratios, separately for rural and urban areas of every Indian state and Union Territory. The poverty counts are computed as the fraction of the population living in households with consumption per head below a poverty line. The poverty lines have been calculated to represent the minimum monthly expenditure per head associated, on average, with a sector-specific minimum calorie intake, recommended by the Indian National Institute of Nutrition. The lines are kept constant in real terms, and are inflated by using two different state-specific price indexes: the Consumer Price Index for Agricultural Labourers (CPIAL) for rural areas, and the Consumer Price Index for Industrial Workers (CPIIW) for the urban sector.

Expenditure data are collected by the Indian National Sample Survey Organization (NSSO) approximately every five years, from a large sample of Indian households interviewed over a one-year period.

Until the 50th round, carried out in 1993-94, all NSS surveys adopted a 30-day recall period for all expenditure items. This choice of recall period is unusual, as most statistical agencies use a shorter reporting period for items that are typically purchased frequently, like food, and a longer period for infrequent expenditures like clothing, footwear, educational expenses, and durables. Several experimental studies find that expenditure reports for frequently purchased items are on average proportionally lower when the recall period becomes longer.


Poverty status in India

Despite splendid achievements, India is still among the poorest nations in the world in per capita terms. It has managed to reduced poverty over that period, but only since about 1975 has the decline becomes fairly steady, albeit slow. And, although the incidence of poverty has declined from 45 to 36 percent between 1950 to 1993-94, population growth caused the number to ballooned up to double in the same period from 164 to 320 million. Of that total three out of four (76 percent) live in rural area.

The NSS 55th round in 2000 indicates that for the year 1999-2000, 23.10 per cent of the people are below the poverty line In absolute numbers it is 2,602,500,000 people. 23.62 per cent i.e. 670.07 lakh persons are urban poor and 27.09 per cent, i.e. 1932.43 lakh persons are rural poor (Government of India, Press Information Bureau). Almost 30 per cent of the population still lives below the poverty line of less than 100 US$ per capita annually (Sengupta, 1992).

In India there are so many people close to the poverty line, the simple headcount ratio, which gets almost all the attention, is extremely sensitive to small changes in both reality and measurement error. Further it would be gross generalization to assume all people living below poverty line are alike.

Indian poverty lines are also differentiated geographically, by state, and by urban and rural households within each state. Thus it is important to point that there is nothing like all India poverty line, either for urban or rural, instead, poverty counts are made for each state, within each sector, and added up to get urban and rural totals. Thus it is imperative to assess poverty at regional level, state level to understand the disparities and analyze who are these poor people and why they are still poor even after more than fifty years of independence.