The simplest and most comprehensive (though arguably not the most accurate or effective) way to enumerate the population is to count every single person. Such a Herculean collection of data, called Census, is usually carried out by the government through interviews and surveys. No estimation is done in it. National Family Health Surveys are conducted in a representative sample of households; National Sample Surveys collect household sample data; Demographic Health Surveys collect nationally representative data on health and population for monitoring, and impact evaluation indicators in the areas of population, health, and nutrition.