The 1990 Census of Population and Housing (CPH), the 9th population census and the 4th housing census conducted in the century, was designed to take an inventory of the total population and housing units in the country and to collect information about their characteristics.
Like all other censuses which are separately documented, the 1990 CPH was designed to gather two major types of data: population and housing. Population data included household membership, overseas contract worker status, relationship to household head, age as of last birthday, sex, marital status, religious affiliation, citizenship, disability, place of residence 5 years ago, literacy and highest educational attainment.
Housing data covered building characteristics like type of building/house, construction material of the roof and outer walls, state of repair, year building was built, floor area of housing unit; tenure status of the housing unit and lot; and presence of household conveniences and land ownership.
While complete enumeration of all households in the Philippines was made, sample households representing approximately 10 percent of the listed households were selected to collect more detailed information. These information were the following: mother tongue; mother's usual place of residence at person's birth; previous place of residence; ability to speak Tagalog/Filipino; language/dialect generally spoken in the household; school attendance; place of school; economic activities; fertility items like the number of children born alive, the number of children still living and the number of children born the past year; and age at first marriage. Additional housing items are sources of fuel for lighting, cooking and drinking water, manner of acquisition and source of financing of housing unit, monthly rental of housing unit and/or lot, type of toilet facility and usual manner of garbage disposal. Definitions of terms and concepts can be found in the explanatory text of the final report.
The enumeration unit was the household. Personal interviews of the head or any responsible member of the household were conducted using CPH Form 2, 3, or 4. A combination of complete enumeration and sampling was employed. Systematic cluster sampling was adopted to select sample households. An enumeration area (EA) consisting of around 300 to 400 households was divided into clusters of five (5) households. The corresponding number of samples of clusters for each EA were obtained based on the following sampling rates:
|Estimated No. of Households in the Municipality||Sampling Rate in the EA|
|1 - 500||100%|
|501 - 1500||20%|
Items relating to the population count and personal characteristics were elicited from all households using the Common Household Questionnaire (CPH Form 2). Sample households were asked the additional questions listed above using Sample Household Questionnaire (CPH Form 3). Institutional households were enumerated using the Institutional Population Questionnaire (CPH Form 4) where all items on population in CPH Form 2 were asked but housing characteristics were excluded.
A post‑enumeration survey called the Census Evaluation Survey (CES) was conducted to determine the extent of under enumeration or over enumeration in the main survey. It was, however, confined to approximately 21,625 households in 180 enumeration areas throughout the country.