|Indicator Name||Poverty headcount ratio at national poverty line (% of population)|
|Long definition||National poverty rate is the percentage of the population living below the national poverty line. National estimates are based on population-weighted subgroup estimates from household surveys.|
|Source||World Bank, Global Poverty Working Group. Data are based on World Bank's country poverty assessments and country Poverty Reduction Strategies.|
|Statistical concept and methodology||Poverty estimates at national poverty lines are computed from household survey data collected from nationally representative samples of households. These data must contain sufficiently detailed information to compute a comprehensive estimate of total household income or consumption (including consumption or income from own production), from which it is possible to construct a correctly weighted distribution of per capita consumption or income.
National poverty lines are the benchmark for estimating poverty indicators that are consistent with the country's specific economic and social circumstances. National poverty lines reflect local perceptions of the level and composition of consumption or income needed to be non-poor. The perceived boundary between poor and non-poor typically rises with the average income of a country and thus does not provide a uniform measure for comparing poverty rates across countries. While poverty rates at national poverty lines should not be used for comparing poverty rates across countries, they are appropriate for guiding and monitoring the results of country-specific national poverty reduction strategies.
Almost all national poverty lines are anchored to the cost of a food bundle - based on the prevailing national diet of the poor - that provides adequate nutrition for good health and normal activity, plus an allowance for nonfood spending. National poverty lines must be adjusted for inflation between survey years to remain constant in real terms and thus allow for meaningful comparisons of poverty over time. Because diets and consumption baskets change over time, countries periodically recalculate the poverty line based on new survey data. In such cases the new poverty lines should be deflated to obtain comparable poverty estimates from earlier years. The data is based on the two most recent years for which survey data are available.
Survey year is the year in which the underlying household survey data were collected or, when the data collection period bridged two calendar years, the year in which most of the data were collected.|
|Development relevance||Estimates of poverty rates and gaps at national poverty lines are useful for comparing poverty across time within but not across countries. See poverty indicators at international poverty lines for comparisons across countries.
For countries with an active poverty monitoring program, the World Bank - in collaboration with national institutions, other development agencies, and civil society - periodically prepares poverty assessments and other analytical reports to assess the extent and causes of poverty. These reports review levels and changes in poverty indicators over time and across regions within countries, assess the impact of growth and public policy on poverty and inequality, review the adequacy of monitoring and evaluation, and contain detailed technical overviews of the underlying household survey data and poverty measurement methods used. The reports are a key source of comprehensive information on poverty indicators at national poverty lines and generally feed into country-owned processes to reduce poverty, build in-country capacity, and support joint work.
An increasing number of countries have their own national programs to monitor and disseminate official poverty estimates at national poverty lines along with well documented household survey data sources and estimation methodology. Estimates from national poverty monitoring programs and the underlying methods used are periodically reviewed by the World Bank.|
|Limitations and exceptions||As with any indicator measured from household surveys, data quality can affect the precision of poverty estimates and their comparability over time. These include selective survey nonresponse, seasonality effects, differences in the number of income or consumption items in the questionnaire, and the time period over which respondents are asked to recall their expenditures.
Because national poverty lines are specific to each country's economic and social circumstances, poverty estimates at national poverty lines cannot be compared across countries, nor can be aggregated to regional or global levels.|
|General comments||This series only includes estimates that to the best of our knowledge are reasonably comparable over time.|