The Family Income and Expenditure Survey (FIES) is a nationwide survey of households undertaken every three years.  It is the main source of data on family income and expenditure, which include among others, levels of consumption by item of expenditure as well as sources of income in cash and in kind.  The results of FIES provide information on the levels of living and disparities in income of Filipino families, as well as their spending patterns.

The FIES is a sample survey designed to provide income and expenditure data that are representative of the country and its 17 regions.  

Starting 2012 FIES, the survey adopted the 2009 Philippine Classification of Individual Consumption According to Purpose (PCOICOP). The 2009 PCOICOP is the first standard classification of individual consumption expenditure in the country. 

The number of families for the FIES was estimated using the household population projections-based on the household population counts from the 2020 Census of Population and Housing (CPH).

The set of samples selected for the FIES is only one of the possible sets of samples of equal size that have been selected from the same population using the same sampling design.  Estimates derived from each of these sets of samples would differ from one another.  Sampling error is a measure of the variability of the estimates among all possible sets of samples.  It is usually measures in terms of the standard errors for a particular statistic.

The standard error can be used to calculate confidence intervals within which the true value for the population can reasonably be assumed to fall.  For example, for any given statistic calculated from a sample survey, the value of that statistic will fall within a range of plus or minus two times the standard error of that statistic in 95 percent of all possible samples of the same size and design.