How to boost response rates to census survey with advanced technology

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Geographic information systems expert Dr Tang discusses how technology can be used to improve census data.


Photo: The U.S. Census Bureau used GIS to study demographic characteristics and lifestyle segmentation data such as income and age / NASA on Unsplash



Starting in late June, the Hong Kong Government will conduct a population census collecting a wide variety of information including basic data such as date of birth and gender and a broader range of demographic, socio-economic, and housing characteristics.


The Hong Kong population census has developed as a result of technological progress in the last two decades. But can we go one step further to make the most out of current technology?


Advanced technology can save manpower 

Census production requires connecting people with places, so an accurate and up-to-date map is a prerequisite. As science and technology evolve, the arduous work of census is made easier by keeping up with the times. 


For example, in the 2001 Population Census, the digital mapping system (DMS) was incorporated for the first time. The DMS used a global positioning system (GPS) and a geographic information system (GIS) that were specially developed for the 2001 Census. The authority provided approximately 100,000 electronic maps with geographic data for the Census, which was convenient for the temporary field workers to locate the household of their assigned interviewees. Electronic maps, now available on mobile devices, can also be used to calculate the distance between locations, which facilitates work allocation by calculating the workload and understanding fieldwork progress. Updated building locations, photos, and sketches, as well as real-time input of collected data can be uploaded to the system, increasing work flexibility.

Simply put, technology has improved efficiency. Although the population has increased from 6.71 million in 2001 to 7.47 million over the past 20 years, and there are more households to be surveyed, only 18,000 temporary field workers are required this time,  as contrasted with 23,000 workers hired in 2001 when digital maps were first introduced.

 When it comes to response rate, segmentation and location matter

 Many countries have also conducted population censuses in the past two years, including the United States. The country has conducted its decennial population census since 1790 and has tremendous experience, especially in using geographic information to optimise their work.

One of the challenges is address verification. With satellite imagery, the authority was able to verify 65% of the addresses in the office, requiring only 35% to be verified in the field. Manpower required was drastically reduced from 150,000 in 2010 to 40,000 last year. What used to take over two hours of work can now be completed in two minutes.

 Another concern which may lower the response rate is personal privacy.

 Today, private and public organisations have scattered personal information. The US Census Bureau has conducted an internal experiment, combining data from commercially available databases with anonymous data from the 2010 U.S. Census. It was found that 52 million people’s names, gender, age, race, and more, could be correctly connected with supposedly ‘anonymous; census data collection. To correct this, the bureau uses mathematical formulas of “differential privacy” for adjusting the census data. By adding slight modifications while using the data, they aim to effectively balance privacy and accuracy. But it is never an easy task. Recently, a group of Harvard researchers has challenged the method, saying the privacy-friendly approach would jeopardize the data accuracy and “negatively impact the redistricting process and voting rights of minority groups.”

 And then, Hong Kong

Social changes in recent years and the COVID-19 epidemic have raised concerns about the public’s response to the census in Hong Kong. How do we encourage a better response among the “hard-to-survey population” who had a less than 50% response in the past? The US experience is a good reference. The US Census Bureau used GIS to study their demographic characteristics, alongside lifestyle segmentation data such as income and age, in order to tailor solutions. 

 Six segments were then identified as follows:

 1.     Dorms to Diplomas (22% response rate): With a median age of 21, university students and recent graduates live in neighbourhoods with a mix of dorms and on-campus/off-campus housing that caters to young renters.

 2.     City Lights (31% response rate): This group earns above-average incomes but lags the general population in net wealth. Its median age is 38.

 3.     Young and Restless (41% response rate): This is a highly mobile group with a median age of just under 30, consisting of people in their early careers who change addresses frequently.

 4.     Modest Income Homes (44% response rate): The labour force participation rate for this group is just 50%, with an income below half of the U.S. median. Within this group, most households rely heavily on public transportation.

 5.     Metro Fusion (45% response rate): Single-parent and single-person households account for more than half of this group, with a median age of 28 and median household income of US$33,000 (the U.S. median household income is US$68,000).

 6.     City Commons (46% response rate): Nearly one-quarter of people in this group receive public assistance or social security benefits. They typically live in large cities and rent apartments in mid-rise buildings.

 According to their characteristics and home address, the authority encouraged participants (via media outlets including emails, leaflets, TV commercials and radio promotions) to respond to the census questionnaires. As a result, the two segments Modest Income Homes and City Commons had an improved response rate of 54%, although they were the least likely to select the web for submitting their responses. For the Dorms to Diplomas segment, which had the lowest response rate of 22% historically, the response rate is now 77%. With the use of advanced technology such as GIS, the census dramatically improved response rates in traditionally hard-to-reach groups.

 In Hong Kong, with the information from census surveys, the government can allocate its resources more efficiently to serve the public, such as locating the inoculation centres for COVID-19 in more accessible locations to facilitate the public and cross border drivers to access community vaccination services. When people start feeling the benefits enabled by the advanced technology, they naturally will respond more enthusiastically.

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