Population Projection by Age and Sex for Macau，1991 to 2001*
Wu Shuo Si(Faculty of Science and Technology University of Macau)
This paper uses the cohort-component method, one of the most common popu-lation-projection techniques, to project the total resident population by age and sex,for Macau from 1991 to 2001. The computations are mainly based on the data obtained from the last two censuses in Macau, the 1981 Census and the 1991 Census. The results show that the total resident population in Macau in the year 2001 will be about 418,119 to 479,235. The paper consists of three sections: (1) Introduction outlines the background for the population projec-tion and briefly explains population change in Macau, some previous research works on population projection for Macau and an evaluation of their results. (2) Population Projection for Macau, 1991 to 2001 shows the calculation of the forward census survival rates, the projection of births, the estimates of age and sex composition of future net migrants, and the projection of total resident population by age and sex, for Macau from 1991 to 2001. (3) Dis-cussion and Conclusion points out that net migration has significantly af-fected the total resident population in Macau. The population growth in this territory can be controlled only when the immigration is under control.
Introduction
According to the last census in 1991, the total population of Macau was 403,038, of which the resident population was 355,693 and the floating population 47,345. About 96.3 percent of the total resident population resided in the peninsula of Macau, and 3.7 percent in the off-shore islands of Taipa and Coloane.1
Although there have been a total of thirteen censuses in Macau, only twelve have been recorded. Table 1 indicates that the first official census was taken in 1866, when the total population was 56,252. In the nineteenth century, the popu-lation in Macau grew steadily. However, there have been four sharp popula-tion increases in the twentieth century: the Civil War in the 1920s and the Sino-Japanese War in the 1940s caused two immigration waves from mainland China to Macau. The Cultural Revolution in China in the 1960s and Macau's eco-nomic boom in the 1980s caused the third and fourth immigration waves to Macau.
Since the next census in Macau will not be taken until 2001, it is necessary to estimate the intercensal population growth and to project the long-term total population. Chou-Soon Wong, Macau Society of Social Sciences, and Deng Hanzeng, Guangzhou Institute of Geography, did population projections for Macau in 1990.2 Based on an estimate of 407,700 for the total population of Macau in 1985 and the low, medium, and high fertility assumptions, they have projected that the total population for Macau in 2000 will be 650,000 to 680,000 as a low projection, 740,000 to 770,000 as a medium projection, and 940,000 to 970,000 as a high projection. Alice Delerue A. Matos, Census and StatisticsDepartment, Macau, has also done similar work.3 Her projection was based on an estimate of 452,300 for the total population of Macau on January 1, 1991 and the assumption of constant birth and death rates. The results of her popu-lation projections in the year 2000 were 608,969 as a high projection, 555,268 as a medium projection, and 501,568 as a low projection. A review of the pre-vious research shows that all the populations estimates used as the bases for the projections were high, because the total resident population enumerated by the 1991 census was only 355,693 (see Table 1). The high estimates of base population have resulted in high projections.
In this paper, based on the most recent data of the 1991 Census of Macau, and taking the significant effects of net migration into account, the cohort-component method has been used to produce a population projection by age and sex for Macau from 1991 to 2001.
After the rapid population growth in the 1980s, the rate of population in-crease in Macau will become steady, because of the strict control of illegal immi-gration. Law No. 2/90/M was enacted in May 1990 by the Macau government after the amnesty of about 35,000 illegal immigrants on March 29, 1990.4 Legal immigrants from mainland China to Macau have been limited to about 1,500 per-sons per year.5 Therefore, it is most unlikely that illegal immigration waves will again increase sharply in the near future. In other words, this is a stable circum-stance for population projection.
Population Projection for Macau, 1991 to 2001
There are usually two basic methods for population projection: the compo-nent method and the mathematical method. The former is more accurate. The method used in this paper is the cohort-component method, one of the most com-mon population-projection techniques. The computations will be carried out sepa-rately for each age and sex group, including (1) the calculation of forward census survival rates by age and sex for Macau from 1981 to 1991; (2) the calculation of alternative projections of male and female births by the period-fertility method for Macau from 1981 to 2001; (3) the calculation of population projection by age and sex for Macau from 1991 to 2001.
Calculation of Forward Census Survival Rates for Macau, 1981 to 1991
The forward census survival rates express survival from a younger age to an old age, the rates being defined in terms of two ages. Hence, there are two time references -- the initial age and date and the terminal age and date. In this sec-tion, we will use the data of the last two censuses in Macau to calculate the sur-vival rates from 1981 to 1991. The formula is defined as follows:6
where 
indicates the ten-year survival rates for a five-year age group x, 
represents the initial population of the five-year age group in 1981, 
represents the terminal population of the five-year age group in 1991: any difference in the date of the two censuses is neglected (the 1981 Census was taken on March 16, the 1991 census August 30). For instance, the rate of the males aged 15 to 19 who will survive in 10 years is calculated as follows:
The calculation of the census survival rates by five-year age-sex groups for Macau, from 1981 to 1991 is summarised in Table 2.
Usually, the census survival rates without net immigration are between 0.0 and 1.0, but Table 2 shows that the census survival rates for several male age groups exceed 1.0, e. g., 
.Similar results are ob-tained for the female age groups. The above figures reflect the significant effects of net migration. The number of net migrants in the decade from 1981 to 1991 was estimated to be 76,858 (see Table 3). Before Law No. 2/90/M was enacted in May 1990, many illegal immigrants from mainland China entered Macau and stayed. On March 29, 1990 the Government granted a general pardon to about 35,000 ille-gal immigrants (note to Table 3).
Table 3 indicates that of 76,858 net migrants 26,798 were male and 50,060 fe-male. But the data on the age and sex composition of the 76,858 net migrants are not available. Based on observation and analysis of the available data of legal and illegal immigrants in the past few years, from 1988 to 1991, one possible way out is to make an assumption about the age and sex composition of those 76,858 net migrants [Columns (4) and (5) in Table 4].
Table 4 indicates that the majority of the net migrants are aged 5 - 49 for both sexes. Consequently, the census survival rates for the respective age groups, 5 -49, exceed 1.0 (see Table 2). Therefore, the effects of net migration should be taken into account. The 76,858 net migrants are subtracted from the census population of 1991 by age groups for both sexes, and then the adjusted census population of 1991 without net migration is obtained [Columns (5) and (6) in Table 5].
After removing the effects of net migration, the adjusted census survival rates are calculated. The results are shown in Columns (7) and (8) in Table 5. These ad-justed census survival rates will be used in the population projection later in the paper.
Alternative Projections of Births for Macau, 1981 to 2001
In addition to the above adjusted census survival rates, the results of birth pro-jection will also be needed in the calculation of the population projection. In this section, the period-fertility method is used to project the number of births in two
consecutive decades, 1981 to 1991 and 1991 to 2001. Three assumptions regarding fertility in Macau during this period are made, representing low, medium, and high alternatives. The low series assumes a ten percent decline of the total fertility rate in the ten years from 1981 to 2001, the medium series a five percent decline in ten years, and the high series a continuation of the total fertility rate from 1981 to 2001. Even though the age-specific birth rates in 1981 are not available, the age-specific birth rates in 1991 are available. Thus, the estimate of the age-specific birth rates in 1981 and the projection of the age-specific birth rates in 2001 can be calculated, using the age-specific birth rates in 1991. The results are summarised in Table 6.
Based on the results in Table 6, the estimated female population by age in 1981 and 1991, and the projected female population by age in 2001 are calculated in Table 11. The estimates and the projections of births from 1981 to 2001 can be calculated. The results are shown in Table 7.
Table 7 shows that the estimated total births in 1981 under the assumption of low fertility is 4,172, which is very close to the registered births (4,207) provided by the Census and Statistics Department, Government of Macau. Therefore, the assumption of low fertility (the birth rate declines ten percent in ten years) in the decade 1981 to 1991 is more reasonable, and this assumption will be used in the population projection from 1991 to 2001.
Based on the results in tables 6and7,the period-fertiliy mehtod7 is applied to estimate and project the total births in the two consecutive decades,1981 to 1991 and 1991 to 2001.The calcuation is summarised in Table 8.
Estimates of Age and Sex Composition of Future Net Migration, 1991 to 2001
Based on the assumption of low fertility rate, and the estimate of net migrants (76,858) in the last decade from 1981 to 1991, and taking the estimated future net migration (1991 to 2001) into account, the population projection by age and sex for Macau from 1991 to 2001 can be calculated by means of the results in the previ-ous section. Because nowadays the Macau government has limited the number of legal immigrants from mainland China to 1,500 each year, and adopted a strict policy to suppress illegal immigration, the number of future net migrants can be assumed to be a certain percentage of the 76,858 net migrants. Three assumptions regarding future net migration from 1991 to 2001 are made, representing low, medium, and high alternatives. The low one assumes 50 percent of the 76,858 net migrants, the medium one 80 percent, and the high one 120 percent. Thus there will be 38,429, 61,486 and 92,230 for the low, medium and high estimates of future net migrants, respectively, for Macau from 1991 to 2001. Based on the statistical data of legal immigration to Macau in 1989, 1990, and 1991,8 the sex and age dis-tribution of the legal immigrants in the three years are calculated and shown in Columns (2) and (3), Table 9. Furthermore, the age and sex compositions of the future net migrants are assumed to follow the same sex and age distribution, and the calculation is presented in columns (4) to (9), Table 9.
Population Projections by Age and Sex for Macau, 1991 to 2001
There are three different results for the population projection by age and sex for Macau from 1991 to 2001 according to the different assumptions of future net migration and a low total fertility rate. One calculation example based on the as-sumptions of low estimate of (38,429) future net migrants and low fertility rate is illustrated in Table 10. All three different results of the population projection are shown in Table 11.
Table 10 indicates that the total number of the resident population in the year 2001 is 418,119 based on the assumptions of 61,486 future net migrants and low total fertility rate.
Table 11 shows that the total numbers of the resident population for Macau in the year 2001 are 418,119, 444,311 and 479,235 respectively, corresponding to the assumptions of low, medium, and high estimate of future net migrants and low total fertility rate.
Discussion and Conclusion
First, the important effects of net migration, particularly illegal immigration, on population growth in Macau was discussed in the calculation process of the adjusted census survival rates in the second section. (For more detailed informa-tion, see D. Y. Yuan's paper on "Illegal Immigration and Urban Living Indicators in Macau".9) Since a significant number of net migrants (76,858) enumerated inthe 1991 census population may cause the census survival rates of many age groups for both sexes to exceed 1.0, the adjusted census survival rates are calculated by means of subtracting 76,858 net migrants from the census population of 1991. Based on the low, medium and high estimates of future net migrants, the projected births, the adjusted census survival rates, and the calculation of population projection have been done. The estimates of the age and sex composition of future net mi-grants are made. (If the more detailed data, such as the age and sex composition of legal and illegal immigrants, are available, it will be very helpful for popula-tion projections).
Second, according to the last two censuses in 1981 and 1991, the total resident population of Macau was 241,729 in 1981 and 355,693 in 1991; the population in-crease in the past ten years was 113,964. In this paper, the projected number of the total residents in Macau in 2001 varies from 449,509 to 453,286. The maximumgrowth in ten years (1991 to 2001) is 479,235 - 355,693 = 123,542 and the minimum growth is 418,119 - 355,693 = 62,426. The results of the projection reveal a low population growth for Macau in the future if net migration is under control. (The same conclusion from a different point of view was made in the author's earlier paper two years ago.10) Therefore, the author would like to suggest that the Macau government pay attention to the control of net migration in order to improve the quality of life.
Acknowledgements
The author would like to express his sincere and grateful thanks to Dr. Vitor Godinho Boavida and Dr. Libânio Martins, Deputy Directors of Census and Sta-tistics Department, Macau; and to Ms. Fátima Choi, Chief of Department of De-mographic and Social Statistics, Census and Statistics Department, Macau, for their valuable and enthusiastic support.
The author would also like to express his appreciation to Professor D. Y. Yuan, Faculty of Social Science and Humanities, University of Macau for his expert ad-vice, and to Mr. Farid Samandari, Faculty of Science and Technology and Ms. Barbara Jean Weissmann, Centre for Pre-University Studies, University of Macau for their helpful comments.
* An earlier version of this paper was presented at the International Seminar on the Population of Macau and the Pearl River Delta, held in Macau on Octobter 20- 22,1993. The main difference between these two papers is that the population projection in the earlier, is based on assumptions of low, medium and high total fertility rates; and the population projection in the revised version is based on assumptions of low, medium and high streams of future net migration.
Notes
1 Census and Statistics Department of Macau, The Population Census of 1991.
2 Chou-Soon Wong and Deng Hanzeng, "Population Projection for Macau,"in D. Y. Yuan, Wong Hon Keong, and Libânio Martins (eds.), Population and City Growth in Macau (Macau: University of East Asia and Macau Census and Statistics Department, 1990), pp. 183 - 190.
3 Alice Delerue A. Matos, "Demographic Forecasts for Macau," in D. Y. Yuan, op. cit., pp. 191 - 207.
4 Govemment of Macau, "Law No. 2/90/M," Boletim Oficial, May 3, 1990.
5 Census and Statistics Department of Macau, Demographic Statistics, 1989,1990, and 1991, Table 8.2.
6 Henry S. Shryock, Jacob S. Siegel and Associates, The Methods and Materials of Demography (New York: Academic Press, Inc., 1976), p. 381. [Condensed edition by Edward G. Stockwell.]
7 Ibid, pp. 447-449.
8 Census and Statistics Department of Macau, Demographic Statistics, 1989,1990, and 1991, Table 8.2.
9 D. Y. Yuan, "Illegal Immigration and Urban Living Indicators in Macau," in Bruce Taylor, D. Y. Yuan, Rufino Ramos, and Wong Hon Keong (eds.), Socioeco-nomic Development and Quality of Life in Macau (Macau: Centre of Macau Studies, University of Macau, and Instituto Cultural de Macau, 1992), pp. 99 - 115.
10 Wu Shuo Si, "The Changing Population of Macau in the Years of 1980s," (M. B. A. thesis, University of East Asia, 1990).
