Annette Prüss-Üstün and Sophie Bonjour
Public Health and Environment
World Health Organization (WHO)
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The percentage of population using solid fuels is the percentage of the population that relies on solid fuels as the primary source of domestic energy for cooking and heating. Solid fuels include biomass fuels, such as wood, charcoal, crops or other agricultural waste, dung, shrubs and straw, and coal.
Note that the presented estimates are actually estimates of the percentage of households in a country using solid fuels in a particular year. The fraction of people exposed was assumed to be the same as the fraction of households using solid fuels. In other words, no attempt was made to adjust population estimates for variations in household size across various settings (e.g. urban households vs. rural households) as such data were not consistently available.
This indicator is calculated as follows: The numerator is the number of people using solid fuels as main cooking fuel (in nationally representative sample) as the main cooking fuel, multiplied by 100. The denominator is the total population (in nationally representative sample).
Limitations of the indicator:
All estimates being modeled for a given year, there might be discrepancies between global and national figures, as national data from different sources are used to model the global figure. Also, values above 95% solid fuel use are reported as “>95%”, and values below 5% as “<5%” to avoid misinterpretation of the precision of the estimates.
Solid fuel use data are routinely collected at the national and sub national levels in most countries using censuses and surveys. Household surveys used include: United States Agency for International Development (USAID)-supported Demographic and Health Surveys (DHS); United Nations Children’s Fund (UNICEF)-supported Multiple Indicator Cluster Surveys (MICS); WHO-supported World Health Surveys (WHS); and other reliable and nationally representative country surveys and censuses.
In the past, with relatively few nationally representative household fuel surveys to use, estimates relied simply on the latest available survey point or used linear regression analysis, with or without covariates at the national level. In recent years, the number of available surveys has increasedsubstantially allowing for more empirical modeling based closely on available data points.
These estimates are based on the WHO Household Energy database (available at http://apps.who.int/ghodata/). This database contains compiled information on cooking fuel use and cooking practices from about 580 nationally representative data sources, that include all Demographic and Health Surveys (Macro International), Multiple Indicator Cluster Surveys (UNICEF), World Health Surveys (WHO) and Living Standards Measurement Studies (The World Bank) as well as national censuses/surveys and national energy statistics.The data draws on already published data sources and WHO thereforedoes not rely on country counterparts for obtaining data.
Unless stated otherwise, solid fuel use (SFU) estimates for a given year were obtained using a multilevel model. The model only accounts for regions, countries and time as a spline function, and SFU estimates were restricted to values ranging from zero to one. For more information on the model, please refer to (WHO, in preparation for publication).
Missing data are estimated based on the following criteria:
The indicator is currently reported for 193 countries with the number of countries for which data are obtained from nationally representative surveys increasing every year.
The population of interest includes the entire population of countries that have a relatively low national income (typically below USD 12,276 per capita).
The time lag between the reference year and actual availability of data series is often about 1-2 years, the time to analyze and publish the data.
The frequency of data production depends on the country; often, new data on use of solid fuels are only assessed once every few years.
Countries are population-weighted to obtain regional aggregates; for countries with no data, the regional mean exposure is assumed; for countries with less than 5% of solid fuel use (SFU), 0% is assumed for the calculation of regional or global means; for countries with more than 95% of SFU, 95% is assumed in the calculation of the mean.
Reporting of estimates by WHO is variable. Updates are produced approximately every two years and made available in the World Health Statistics Series :