The Corn Production Survey (CPS) 2016 covered the April 2016, July 2016, October 2016 and January 2017 Rounds of the 62nd year of the quarterly survey. CPS is one of the two modules of the Palay and Corn Production Survey (PCPS). The other module is the Palay Production Survey (PPS). The generation of production statistics on palay and corn through the quarterly Rice and Corn Production Survey (RCPS), now known as the Palay and Corn Production Survey (PCPS) dates back to as early as 1954 when the former Bureau of Agricultural Statistics (BAS) was still a division (Agricultural Economics Division) of the then Department of Agriculture and Natural Resources (DANR).
The RCPS has for its predecessors, the Crops and Livestock Survey (CLS), 1954-1968; the Integrated Agricultural Survey (IAS), 1968-1985; and the Rice and Corn Survey(RCS), 1985-1993. Prior to 1986, the RCS employed a two-stage stratified sampling design with municipality as the domain. In 1986, the RCS adopted a three-stage sampling design with province as the domain. In 1989, the RCPS design evolved from a statistical research undertaken jointly by the former Philippine Statistical Association (PSA), now known as Philippine Statistical Association, Incorporated (PSAI) and former Bureau of Agricultural Statistics (BAS) under a grant from the USAID. It was conceived as an improvement to the RCS with a completely different sampling frame and design.
The new RCPS design was officially adopted in July 1994. The design used the results of the 1991 Census of Agriculture (CA) as basis for sampling frame and is still being implemented up to the present. Despite the long history of this quarterly survey, it was continuously improved in design and contents. Thus, in 2007, an updating of the list of farming households in the CPS sample barangays was made. Consequently, a new set of sample households was drawn. Likewise, modification in the contents of the survey was made and implemented in December 2007 (January 2008 Round). Also, starting this round, the name of the survey was changed to Palay and Corn Production Survey (PCPS).
The improved Corn Production Survey, January 2008 Round, underwent further changes on sample status and terms and concepts used. Hence, revisions of the questionnaire were made and a supplementary manual of instruction was provided for the CPS April 2008 Round.
The continuous efforts in developing approaches and methodologies in estimating corn statistics had been done, particularly, the CPS questionnaire. As early as 2010, the proposed revision of the CPS questionnaire was included in the work plan of the working group on cereal statistics. In the succeeding quarterly meetings, the group reviewed the current CPS questionnaire and made sure that the same items were included in the proposed questionnaire. The pre-test was conducted in June 2011. The issues encountered, recommendations/suggestions and agreements by the working group on the pre-test of the questionnaire and those raised during the National Management Consultative Meeting (NMCM) held last June 2011 were presented to the body for assessment. Refinements were made in the questionnaire based on the results of the assessment. The major features of the new sets of questionnaires are: shift from barangay level to farm level questionnaire i.e., from a maximum of five (5) households to one (1) household per questionnaire; change in questionnaire format; more detailed sample status categories; defined types of corn; inclusion of items on labor inputs; and application of organic pesticides. These new sets of questionnaires were implemented starting April 2012 survey round of the CPS.
The Corn Production Survey is one of the two modules of the Palay and Corn Production Survey (PCPS), formerly known as the Rice and Corn Production Survey (RCPS). The Corn Production Survey (CPS) is a quarterly survey conducted by the Philippine Statistics Authority (PSA). It aims to generate estimates on corn production, area and yield and other related information at the provincial level. The four rounds are conducted in January, April, July and October. Each round generates estimates for the immediate past quarter and forecasts for the next two quarters. Results of the survey serve as inputs to planners and policy makers on matters concerning the corn industry.
Kind of Data
Sample survey data [ssd]
Unit of Analysis
The scope of the Corn Production Survey includes:
- Production, area planted/harvested and yield by crop type and seed class
- Usage of seeds, fertilizer and pesticides
- Source of irrigation water and adequacy
- Monthly distribution of production and area harvested
- Farm household disposition of production
- Area with standing crop
- Planting intention for the quarter
Agriculture, forestry, fisheries
Philippine Statistics Authority
Methodology of data collection, processing, dissemination and analysis
Philippine Statistics Authority
Farming households in the barangays.
Producers and sponsors
Philippine Statistics Authority (PSA)
National Economic and Development Authority (NEDA)
Government of the Philippines
The sampling procedure used in the Corn Production Survey (CPS) 2016 was first implemented in 1994. This is a replicated two-stage stratified sampling design with province as the domain, barangay as the Primary Sampling Unit (PSU) and farming household as the Secondary Sampling Unit (SSU).
The results of the 1991 Census of Agriculture and Fisheries (CAF 1991) serve as sampling frame at the PSU and SSU levels. In the said census, the largest barangay in a municipality is taken with certainty while a 50 percent sampling rate is used for selecting the remaining barangays in the municipality. This scheme effectively resulted in the generation of two sub-universes: a sub universe of barangays with probability of selection equal to one (these barangays are called 'certainty barangays') and another sub-universe of barangays with probability of selection equal to 0.5. This characteristic of the CAF 1991 data is used in the selection of sample barangays for the CPS.
The barangays are arrayed in ascending order based on corn area which are stratified such that the aggregate corn area of the barangays belonging to one stratum is more or less equal to the aggregate corn area of the barangays in any other stratum. Ten strata are formed for major corn producing provinces and five for minor producing provinces. In all these provinces, the last stratum consisted of the certainty barangays per CAF 1991 design.
For each stratum, four (4) sample barangays are drawn independently using Probability Proportional to Size (PPS) sampling with the barangay's corn area as size measure. This resulted with four (4) independent sets of barangays (i.e., four replicates) for the province. Systematic sampling is used in drawing the sample farming households in each sample barangay.
For economic reasons, sample size per barangay is limited to a minimum of four (4) and a maximum of twenty-five (25). To correct for this limitation of the design, the use of household weights is instituted. A detailed discussion of weighting in the CPS is included in the survey's estimation procedure attached as a Technical Document.
In November 2007, an updating of the list of farming households in all corn sample barangays nationwide was done to address the problem of non-response due to transfer of residence, stoppage of farm operation, passing away of operator etc. Consequently, a new set of sample households was drawn.
Respondents who refused to be interviewed, not home, unknown and transferred to another barangay are treated as missing and are replaced at the central office for the next quarter's survey. The replacement samples are taken from the list of replacements (farming households) for the barangay and are reflected in the list of sample households for the next round.
CPS 2016 registered response rates which averaged 74.28% across its quarterly surveys - April 2016 Round, July 2016 Round, October 2016 Round and January 2017 Round.
Sample weights are applied to all variables at the household-level. These are determined as a function of the uniform raising factor for the province, denoted by Rk, and the adjusted household weights.
Rk is initially computed from the following characteristics: average total area planted to corn per stratum, average total area planted to corn per barangay, average number of farming households per barangay, average number of sample farming households per barangay and average number of sample barangays per stratum.
Sample size for the sample barangay is determined based on the following information: Rk, total number of farm households in the sample barangay, total palay area of the sample barangay, aggregate palay area in the stratum and number of sample barangays in the stratum.
For operational purposes, sample size per barangay is limited to a minimum of four (4) and a maximum of 25. To correct for this limitation, the use of a uniform sample weight for all sample households in the same sample barangay is instituted. Household weights are determined as a function of the computed sample size and the 'desired' sample size for the barangay, that is:
a) 1.00 if the computed sample size was between 4 and 25;
b) less than 1.00 if computed sample size was less than 4
c) more than 1.00 if computed sample size was more than 25, and
d) based on computed sample size and number of farming households in the barangay if computed sample size is less than 25 and said sample size is greater than total number of farming households in the barangay.
Household weights were encoded together with other household level data. During table generation, weighting adjustment was done to correct for sampling unit non-response due to the following reasons:
- refusal of target respondent or any othe knowledgable household member to be interviewed
-sample barangay was not accessible during the survey period
-entire household was temporarily away during the survey operation-
-sample household has transferred residence to another barangay
- sample household's residence could not be located / unknown in the sample barangay
Weighting adjustment was done for each sample barangay, whenever applicable. This was calculated by multiplying the original household weight by the reciprocal of the response rate. Response rate is the ratio of the number of sample households who responded to the survey (either corn household and non-corn household) to the total number of sample households in the barangay. Calculation of the final weight was done afterwards, by multiplying the adjusted weight by the uniform raising factor Rk.
Details of the above discussion on weighting adjustment procedures, are contained in the document describing the Corn Production Survey (CPS) sampling methodology provided as a Technical Document.
Dates of Data Collection
April 2016 Round
July 2016 Round
October 2016 Round
January 2017 Round
Data Collection Mode
Face-to-face paper [f2f]
Prior to data encoding, the accomplished survey returns are manually edited and coded. Manual editing is checking of responses to the Corn Production Survey (CPS) questionnaire in terms of acceptability and validity. This activity aims at improving the quality of data collected by the SRs. It involves the checking of data items based on criteria like completeness of data, consistency with other data items and data ranges. Coding is the assignment of alpha-numeric codes to questionnaire items to facilitate encoding.
Encoded data are subjected to computerized editing using a customized editing program. The editing program take into consideration the validation criteria such as validity, completeness and consistency with other data items. This activity is done to capture invalid entries that were overlooked during manual editing. An error listing is produced as output of the process. The errors reflected in said lists are verified vis-à-vis the questionnaires. The data files are updated based on the corrections made. Editing and updating are performed iteratively until a clean, error-free data file is generated.
Completeness check is done to compare the data file against a master file of barangays to check if the sample barangays have been completely surveyed or not. This activity is done after a clean, error-free data file is generated.