Technical Notes

Technical Notes on the Seasonal Adjustment of CPI


Consumer Price Index (CPI) provides a general measure of the changes in average retail prices of commodities bought by specific group of consumers in a given area and in a given period of time. It mainly measures the composite change in the retail prices of the various commodities over time.


The seasonal adjustment of a time series mainly refers to the isolation of seasonal fluctuations, leaving the basic trend of the observed series. Seasonal fluctuations can be due to composite effect of climates and institutional events which repeat more or less regularly each year. Specific factors that may affect the CPI include seasonality due to production cycles, demand due to school year or holidays, and practices such as increase in rental rates during the beginning of the year. After the removal of seasonal variations, the resulting series is referred to as the seasonally adjusted series or the deseasonalized series. By removing the effects of seasonality on the CPI series, analysis can be made on a month-on-month basis. Thus, seasonal adjustment allows comparisons over recent months and gives short-term trend movements for the series. In general, if seasonally adjusted CPI levels are lower than the unadjusted series, it means that seasonal factors push up prices relative to the expected trend.


The over-all CPI is tabulated using six major commodity groups in the Philippines, Metro Manila (MM) and Areas Outside Metro Manila (AOMM). The six groups are: Food, Beverages and Tobacco; Clothing; Housing and Repairs; Fuel, Light and Water; Services; Miscellaneous. The last five groups listed comprise the non-food items. Initially, the CPI series for all items as well as the Food, Beverages and Tobacco (FBT), and non-food items for MM and AOMM were tested for the presence of seasonality assuming stability. In MM and AOMM, presence of stable seasonality were observed both for FBT and Non-food items. However, the CPI for all items indicated that there is no seasonality in the series mainly due to the exhibited opposite direction of peaks and troughs of the FBT and non-food items, thus, canceling out. Presence of stable seasonality though, was observed both for FBT and non-food items when analyzed separately. The current seasonally adjusted series are based on X11ARIMA88 built-in model (Multiplicative with log-transformation (0,1,1)(0,1,1) and Additive (0,1,1)(0,1,1)) fit to the 2001 data series.

Technical Notes on the Annual Poverty Indicator Survey (APIS)


The Annual Poverty Indicator Survey (APIS) is a nationwide sample survey designed to provide information on the different indicators related to poverty. This survey is a joint undertaking of the National Statistics Office, World Bank Mission and the United Nation Development Program.

Survey Objectives

The APIS aims to provide inputs to the development of an integrated poverty indicator and monitoring system which would enhance timely, accurate and consistent production of poverty-related data that can be used at the national level.

Technical Notes on the 2000 Census of Population and Housing (CPH)

The 2000 Census of Population and Housing otherwise known as Census 2000 is the 11th census of population and the 5th census of Housing to be undertaken in the Philippines since 1903. Prior to this period, in 1570 to 1800s, the population count was determined largely by estimates rather than actual counts. In particular, the population was based on the number of tributes comprising an encomienda in 1591. In the succeeding years, when the people were distributed by parish among religious orders, the population estimates depended on church records (baptism, marriages and burials) and were limited to the Christian population.
The first official census in the Philippines was carried out in 1878 by the Spanish government, followed by the census of 1888 and 1898.
Census 2000 was designed to take an inventory of the total population and housing units in the Philippines and to collect information about their characteristics. The census of population is the source of information on the size and distribution of the population as well as information about the demographic, social, economic and cultural characteristics. The census of housing, on the other hand, provides information on the supply of housing units, their structural characteristics and facilities which have bearing on the maintenance of privacy, health and the development of normal family living conditions. These information are vital for making rational plans and programs for national and local development.

Subscribe to RSS - Technical Notes