人口資料是國家施政的基礎，大多數國家會以普查（Census）為全國性資料的主要蒐集方法，但近年戶口普查遭遇不少挑戰，許多國家考量不進行全國普查，改以其他方法取得資料品質可媲美普查的全國人口估計值。美國、法國的滾動式普查是方法之一，每年輪流抽取3%不同的樣本，除了可取得不錯的資料品質，又能獲得五年連續調查結果，打破十年一次靜態人口的限制。

本文也以探討普查替代方法為目標，評估以健保就醫資料取得我國國民經常活動資料的可行性，比較幾種常見的常住地判斷方式，包括感冒就醫、以及本文提出的幾種方法，評估哪種方法較能反映國人就醫地區的特性，並討論未來以健保就醫作為取得常住人口時，必須考慮的配套措施及限制。另外，我們也將常住地判斷方法應用於探討人口遷移，將立委選區訂為分析單位，以避免人數差異太大的問題，分析發現臺灣大致可分為幾個生活圈，其中有幾個地區的遷入及遷出相對活躍。

Censuses are usually the only method for collecting information on a national population, and they are conducted every ten years for most countries. Taiwan's government also conducts censuses every ten years to collect information on the de jure population, covering the shortage of the household registration system. However, there are potential problems in the traditional census, such as low response rates, poor data quality, outdated information and rising survey costs. Taiwan, like a lot of countries, has been seeking alternative methods for collecting national data and decided to use sampling surveys (of about 16% of the national population) to replace the whole population census in 2010 and 2020, in order to cope with the problems of low response rates and rising survey costs. Still, the sampling survey cannot provide timely population information in Taiwan. The rolling census is one of the new methods which can offer up-to-date information, and was first adapted by the U.S. and France in 2010. The rolling census in the U.S., American Community Survey, collected data on 3% of the national population annually for five years, and this can deliver a time series of national estimates for those five years.

In this study, we aim to explore new data collection methods which can serve as an alternative to the traditional census and provide timely population information. In particular, our goal is to evaluate the possibility of using data from the National Health Insurance (NHI) Research Database for acquiring information on the de jure population in Taiwan. In particular, we use the Longitudinal Health Insurance Database 2005 (LHID2005) in this study. In addition to records on upper respiratory tract infections, we also propose three other methods based on the records of outpatient visits to identify the place of normal residence. We choose outpatient rates and other criteria from the NHI data for method evaluation, and find that the medical cost of outpatient visits less than 555 points (one point is close to one New Taiwan Dollar) is the most appropriate method.

To demonstrate the feasibility of using NHI data to acquire the population information, we apply the proposed methods to explore the domestic migration in Taiwan. The official records of Taiwan's domestic migration are available only at the level of province and special municipality, and are not accessible for counties and townships. To make up for the deficiency of official records, we estimate the domestic immigrants and emigrants at the level of electoral circumscription (73 seats) for members of the Legislative Yuan. The population of each electoral circumscription is between 200,000 and 500,000, smaller than that of counties and larger than that of townships. The results show that the domestic migration in Taiwan can be separated into three sub-regions: northern, central, and southern Taiwan. The migration activities are active within each region, but not as active between regions. Also, the six major cities (or special municipalities) in Taiwan, each with population of at least two million, attract most of the domestic immigrants, and the remote areas (such as eastern counties) have the highest emigration rates.