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Q.How often are population projections revised?

The NDC prepares new long-range population projections once every two years. They take account of the latest fertility, mortality and migration situations, and are provided for open reference and use. 

Q.Why does the timeframe for population projections need to go beyond 10 or 20 years ?

Although policies relating to national development mostly have a long-range perspective of 10 years, countries around the world usually produce population projections for 30-50 years into the future. This is because the size and age structure of the population in the next generation depends on the numbers for fertility, mortality and migration in the present generation, and the longer range projections are made to inform us how the birthrate in the current generation will change the age structure of the next generation from childhood to old age. Some countries even make projections for 100 years ahead, to track the age structure of the future population under specific scenarios of stable growth. The NDC has given consideration to the timeframe of other countries’ population projections, and has decided to run the latest projections up to 2065 so that they are comparable to indicators relating to future population in the international sphere.

Q.What is the scope of the population projections? Do they include foreigners who work or study in Taiwan?
  1. The figures for population, fertility, mortality and migration in this report refer to ROC citizens who reside in and have established household registration in Taiwan. They include foreign nationals who have obtained household registration status in Taiwan, but do not include foreigners who reside in Taiwan for work or study.
  2. Because Taiwan’s official statistics for population, labor, etc., use the population with household registration as their statistical subjects, important demographic indicators such as the fertility rate, aging index, and unemployment rate, do not include foreigners who stay in Taiwan for work or study. Though our country’s census data furnishes statistics on the population actually living in the country (i.e., the resident population), the frequency of its update is just once in ten years, so the data loses contemporaneity. Furthermore, in order to be able to use historic data for conducting comparison and trend analysis, and to avoid producing inconsistencies with the statistical subjects of common population indicators, the NDC’s population projections also correspondingly use as subjects ROC citizens who reside in and have established household registration in Taiwan.
Q.Is there also population projection data for each county and city? How can this be obtained?
  1. The NDC’s population projections are primarily data by age and gender for the Taiwan Area, and do not include projections for individual counties and cities. Since inter-regional population migrations are a key factor affecting population size in an individual locality, and with the limitation of available data for population projections, the NDC uses household registration population data as the basis for its projections. But because there are often great disparities between the household registered population of an area and the size and age structure of the population that in actuality is ordinarily resident in it, it would hardly be possible for projections to deliver a true reflection of local population changes, hence the NDC does not currently aim to provide population projections for individual counties and cities.
  2. When projecting total population development trends in individual counties and cities to provide as reference for county and city governments’ land use planning, the Ministry of the Interior bases these on the NDC’s population projections, while taking into consideration each county and city’s current population, residential attraction, transportation costs, industrial development status, etc. But this data can only provide an indication of each county and city’s future total population, and cannot provide a breakdown of its structure by age, gender, etc. The results of population projections for each county and city can be viewed in detail in the Nationwide Regional Planning section of the website of the Construction and Planning Agency, Ministry of the Interior, at https://goo.gl/HF2U51.
Q.What method does the NDC use for population projections?

The NDC mainly uses the cohort-component method, which is the method in general use internationally. Starting with the base-year end-of-year household registration population divided into age-sex cohorts, using 1-year groups for the age cohorts, and inputting fertility, mortality and net international household registration migration data, with each person’s age increasing year by year, this method yields projections for the future population of males and females of each year of age. Projections for fertility, mortality and net international household registration migration are respectively obtained by using relevant statistical methods, expert-postulated scenarios, and so on.

Q.Are population projections in effect predictions of future population numbers?
  1. A "prediction" is a general statement of what might be expected to happen in the future, essentially a conjecture about future events before they occur. A "projection" is the result of an estimation of what will happen under specified conditions or circumstances. A "forecast" is a scientific, objective assessment of what is likely to happen in the future based on past data and current circumstances, presenting a certain degree of predictive reliability, and usually used in relation to weather.
  2. Population projections cover a relatively long time-range, are based on determining the situation of fertility, mortality and migration as the three main factors in population change, and are derived from estimation under hypothetical scenarios of possible future situations (usually using high, medium and low variant scenarios), to be used as bases of reference for policy planning. Hence, they are not predictions or forecasts of future population.
Q.What are meant by high, medium and low projections?
  1. Since the number of births is a key factor in deciding the future population size, the NDC uses three differing fertility assumptions, with high, medium and low fertility variants, in its fertility projection model, and matches these with future projections of mortality and migration to obtain high, medium and low projections for the future population.
  2. The NDC considers how other countries set their assumptions for future birth rate, with the high variant assuming that our citizens will become more willing to raise the next generation, and so reverse the downward trend of the birth rate; the medium variant assuming that the total birth rate will remain at its present level, and mainly due to our country’s long-term ultra-low birth rate, assuming that under the inertia effect, related government policies will only be able to arrest the birth rate’s downtrend,  and will hardly be able to turn it back upward; and the low variant assuming that the phenomena of our citizens marrying and reproducing late or not marrying and not reproducing will persist, so that the birth rate will continue to fall.
Q.Is there population related data for the past?
  1. This inquiry system is mainly intended for the provision of data relating to future population projections, but to aid analysis and comparison of future and past population related data, the NDC also compiles historic population data in the appendices to the population projection reports, and these can be downloaded for reference in the “Report Download” area of this system.
  2. If you wish to delve further into more population related data, you can visit the web pages of the Ministry of the Interior’s Department of Statistics.