Interesting Discovery from HK Projected Population (Update 1)

Recently hall mates have been disturbed by the trend of the population proportion by sex in HKU and the real proportion of our hall. Girls seem to be much more than boys in the years to come. However, some of the students take the reference on the present “Hong Kong Resident Population by quinquennial age group, sex and whereabouts at reference moment” , 2006, and argue that since number of boys in the age group 15-19 and even 10-14 is much larger than that of girls, the future trend of proportion by sex will reverse in the university, i.e. the university will enroll more boys than girls.
The conclusion seems to be persuasive under the support of data. However, it is a common misinterpretation of data. The misinterpretation is not on whether the population of whole Hong Kong residents can be used to mimic the population in HKU is questionable per se. It is the static use of dynamic data in the centre of the question.
The assumption of the previous conclusion is that the proportion of residents by sex will not change as they grow over the years. This may be true to some of the age groups. However, in HK, it is definitely not the case for age group of 15-24.
From the same source, government of Hong Kong provided the “Projected mid-year population by age group and sex, 2007-2036” . A close check on those projected data, you can find that for all those years, age group of 15-19 has the property of more boys than girls. However, more girls are predicted in age group of 20-24 than boys. For instance, there will be 215.3 thousand boys and 207.1 thousand girls in age group 15-19. On the contrary, there will be 222.8 thousand boys and 278.0 thousand girls in age group of 20-24. After 5 years, in 2017, the numbers of boys and girls in age group 15-19 are 170.6 and 162.2 thousand separately. However, the numbers in age group 20-24 will be 212.1 and 272.8 thousand separately.
The above evidence shows that the population of age group 15-19 is not necessarily become the population of age group 20-24. The difference between boys and girls will change dramatically. A detailed look at the dramatic change is the sudden increase of female at age group 20-24.
A good explanation of this sudden increase can be found in “Hong Kong Resident Population by Duration of Residence in HK, Ethnicity, Quinquennial Age Group and Sex, 2006Hong Kong Resident Population by Duration of Residence in HK, Ethnicity, Quinquennial Age Group and Sex, 2006” (called New Resident Population in the following) which gives us the detailed number of new residents in HK by age group and sex. At the year 2006, the number of new residents who have lived in HK from 1 year to 5 years in age group 20-24 is 38282. Among these new residents, only 4797 are male and the rest 30000 plus are female. That means the new residents are mainly female which convert the difference of male and female at age group 14-19 5 years ago.
The more interesting thing can be found by decomposed the ethnicity of these new residents. It will help to proof the other falsification of assumption: the population of whole Hong Kong residents can be used to mimic the population in HKU.
Following are part of the data from “New Resident Population”:
Duration in HK <1year:
Age group/Sex Chinese Filipino Indonesian Japanese Nepalese Thai Indian
20 - 24 Male 1262 31 1 10 40 - 52
Female 1758 2923 6535 40 40 52 108
Both sexes 3020 2954 6536 50 80 52 160
Duration in HK from 1 to 2 years:
Age group/Sex Chinese Filipino Indonesian Japanese Nepalese Thai Indian
20 - 24 Male 505 11 10 21 40 - 30
Female 987 1513 5285 10 96 38 153
Both sexes 1492 1524 5295 31 136 38 183
Duration in HK from 2 to 3 years:
Age group/Sex Chinese Filipino Indonesian Japanese Nepalese Thai Indian
20 - 24 Male 524 14 30 10 42 - 20
Female 891 1034 3885 10 60 60 30
Both sexes 1415 1048 3915 20 102 60 50
Duration in HK from 3 to 4 years:
Age group/Sex Chinese Filipino Indonesian Japanese Nepalese Thai Indian
20 - 24 Male 684 - - - 21 - 1
Female 899 500 2642 - 104 55 10
Both sexes 1583 500 2642 - 125 55 11
Duration in HK from 4 to 5 years:
Age group/Sex Chinese Filipino Indonesian Japanese Nepalese Thai Indian
20 - 24 Male 851 10 - - 19 10 10
Female 1197 315 1397 - 111 23 5
Both sexes 2048 325 1397 - 130 33 15
It is quite clear that in most years new residents are from Indonesia, China and Philippines. Apart from some of the Chinese new residents who are pursuing bachelor degree in HK due to the agreement and policies between Mainland China and HKSAR, most of the new residents may not study in a university. The inflow of so many Indonesian and Philippines are mainly digested in the domestic service industry and restaurant industry. As a result, the population of whole Hong Kong residents cannot be used to mimic the population in HKU.