NSCB - Executive Board - Resolution No. 1-ADOPTION OF THE METHODOLOGY USED IN GENERATING THE 2000 CENSUS OF POPULATION AND HOUSING-BASED NATIONAL POPULATION PROJECTIONS

NSCB Resolution No. 1
Series of 2005

A Brief Description of the Methodology for the
2000 Census-Based Population Projections

Annex BR-01-2005-01

The 2000 Census-Based Population Projections basically utilizes the Cohort-component Method. This methodology relies on the fact that population change is the result of the demographic processes fertility, mortality and migration. The last component, migration, is generally not considered at the national level of population projections since it is assumed that international migration has still relatively little effect on the national total population.

A. Base Population

The population counts served as the base population by age, sex and province from the 2000 Census of Population and Housing or Census 2000. The age-sex data were evaluated before these were used for the generation of the base population. The indexes that were used to measure the quality of the age-sex data from the Census 2000, which include the UN Age-Sex Accuracy Index, Myer’s Index, Whipple and Bachi Methods, revealed, minimal age heaping and digit preference, except for ARMM provinces. The Inter-Agency Working Group on Population Projections (IAWGPP) also noted that in 58 out of 79 provinces, the proportion of population in the age group 0-4 was smaller than that for age group 5-9. Census survival ratios, fertility rates and internal migration rates were examined to see if this phenomenon was plausible. The group concluded that fertility in these provinces is still high so that the population in age group 0-4 should comprise the largest proportion of the provincial population. The most probable reason for the unexpected result is an undercount of children below one year of age. Hence, estimates of the total fertility rate (TFR) and age specific fertility rates (ASFRs) from the 1998 and 2003 National Demographic and Health Surveys (NDHS) were used to derive the number of births in the year prior to May 1, 2000 in order to obtain an estimate of Po (population 0-1) as of the Census 2000. The difference between the estimated Po and the enumerated Po in Census 2000 was 146,582. This number was added to the July 1, 2000 population aged 0.

The May 1, 2000 population by age and sex for all provinces were forward-survived to July 1, 2000 using the population growth rate of each province from May 1, 1990 to May 1, 2000. The national population as of July 1, 2000 is the sum of the provincial populations. This procedure is in line with the conventional practice to use July 1 as the reference date when preparing population projections. The 146,582 difference in Po was distributed to all provinces based on their population size except for NCR and the ARMM provinces. The age-sex data of the ARMM provinces were “smoothed” for age-misreporting.

B. Fertility

The IAWGPP adopted the regional estimates of TFRs and ASFRs from the 2003 National Demographic and Health Survey, which are shown in Table 1, as the baseline fertility rates.

Table 1. Age-Specific Fertility Rate and Total Fertility Rate,
Philippines: 2003 NDHS

Age Group	Age-Specific Fertility Rate
15-19	0.053
20-24	0.178
25-29	0.191
30-34	0.142
35-39	0.095
40-44	0.043
45-49	0.005
Total Fertility Rate	3.54

For future trends of fertility, three assumptions were made; these are stated in terms of the time when replacement-level fertility, that is NRR of 1.0, will be attained. For the LOW series (rapid pace of fertility decline), NRR of 1.0 was targeted for the year 2030. For the MEDIUM series (moderate pace of fertility decline), NRR of 1.0 was targeted for the year 2040 and for the HIGH series (slow pace of fertility decline), an NRR of 1.0 by year 2050. An NRR of 1.0 has a corresponding TFR of 2.0. Table 2 shows the projected TFRs under the three assumptions.

Table 2. Projected Total Fertility Rates in the National Projections
Under Varying Assumptions

Period	LOW	MEDIUM	HIGH
2000-2005	3.37	3.41	3.44
2005-2010	3.07	3.18	3.25
2010-2015	2.79	2.96	3.07
2015-2020	2.54	2.76	2.9
2020-2025	2.31	2.57	2.74
2025-2030	2.1	2.39	2.58
2030-2035	1.91	2.23	2.44
2035-2040	1.73	2.07	2.31
2040-2045	1.58	1.93	2.18
2045-2050	1.43	1.8	2.06

Note: NRR=1.0 is targeted for the year 2030 for the low series,
2040 for the medium series and 2050 for the high series

C. Mortality

The PEOPLE software was used in preparing the population projections. This software requires life expectancy at birth ( ) as input for mortality indicator. This indicator can be derived from a life table. The construction of a life table from the latest available age-specific death rates (2000 Vital Statistics) for males and females is necessary. These death statistics were adjusted for under registration. At the national level, the level of completeness of death registration was estimated using the Preston and Coale Method. The life table estimates of the life expectancy at birth ( ) for males and females were utilized as baseline values.

The for the projection periods were calculated using the UN Model for the quinquennial gains in life expectancy (Table 3), following a moderate increase in survivorship.

Table 3. Working Model for Mortality Improvement,
Quinquennial Gains (in years) in Life Expectancy at Birth (e00)
According to Initial Level of Mortality

Initial Mortality Level (e 0 0 , in years)	Fast		Middle		Slow
Initial Mortality Level (e 0 0 , in years)	Male	Female	Male	Female	Male	Female
55.0-57.5	2.5	2.5	2.5	2.5	2	2
57.5-60.0	2.5	2.5	2.5	2.5	2	2
60.0-62.5	2.5	2.5	2.3	2.5	2	2
62.5-65.0	2.3	2.5	2	2.5	2	2
65.0-67.5	2	2.5	1.5	2.3	1.5	2
67.5-70.0	1.5	2.3	1.2	2	1	1.5
70.0-72.5	1.2	2	1	1.5	0.8	1.2
72.5-75.0	1	1.5	0.8	1.2	0.5	1
75.0-77.5	0.8	1.2	0.5	1	0.3	0.8
77.5-80.0	0.5	1	0.4	0.8	0.3	0.5
80.0-82.5	0.5	0.8	0.4	0.5	0.3	0.3
82.5-85.0	-	0.5	-	0.4	-	-
85.0-87.5	-	0.5	-	0.4	-	0.3

Note: Lower limit is inclusive of the value while upper limit is exclusive of the value.
E.g. the range 65.0-67.5 means from 65.0 to less than 67.5
Source: United Nations (1989), 1988 World Population Prospects, Table 1.4

The present population projections use one mortality assumption. Under this mortality assumption, the projected values of for the country are shown in Table 4.

Table 4. Projected Values of Life Expectancy at Birth
by Sex, Philippines: 2000-2040

Period	Life Expectancy at Birth
Period	Male	Female
2000-2005	64.1	70.1
2005-2010	66.1	71.6
2010-2015	67.6	73.1
2015-2020	68.8	74.3
2020-2025	70	75.5
2025-2030	71	76.5
2030-2035	72	77.5
2035-2040	73	78.3

This single set of projected values of life expectancy at birth in combination with the three sets of fertility rates were used to project the population up to the year 2040.


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