This article is part of the "Fragmented" - where I did preliminary data exploration just for fun, but later may be developed into a more comprehensive review. This piece was originally published on my personal Facebook.
Webb proposed that since the National Security Law was imposed in Hong Kong, 1 in 57 people (a very specific number) has left Hong Kong, presumably long-term, if not permanently.
While this is an interesting observation, we couldn't be sure that it is the result of the NSL. Perhaps one of the most obvious alternative explanation is these results are simply representing foreign citizens returning home because of the pandemic. Here are my two cents on how we could further investigate how many Hong Kongers have actually left (for good) since the NSL is being imposed, and whether it reflects the "mass migration wave" as suggested by Webb and peers (Confirmation bias warning: I think it is. )
To explore the underlying relationship between NSL and departure of Hong Kongers, we could begin with exploring the recent statistics of VISA and/or Passport (HKSAR/BNO) applications between Jul-Dec 2020, and compare them with the data of the same period in earlier years. In the following example, I picked 2016 for two simple reasons: the People's Satisfaction with the HK Government (As conducted by the University of Hong Kong) is that the score at that time is relatively stable (see that flat line), and this particular period is neither too close or too far away from the post-2014 Umbrella Revolution, the 2019-2020 Protest and the legislation of the NSL. These "VISA" data are arguably a better proxy to understand the effect of NSL on the hypothesised migration wave than using only the travellers' statistics.
The purpose of this article is solely written as a proof-of-concept article, therefore I have only included the data of Taiwan (good job on open data!), and hopefully, it could provide a brief idea of the mass migration wave (and whether it exists or not).
Taiwan is long known for its support to the protesters in Hong Kong, therefore a popular destination for Hong Kongers. Here we could see:
Long-term (6mths) stay /
> Jul - Nov 2020: 6,340 (+3,450)
> Jul - Nov 2016: 2,890
Migration (Settlement) /
> Jul - Nov 2020: 675 (+149)
> Jul - Nov 2016: 526
So here we are presenting the first piece of the many evidence of a potential mass migration. At a glimpse, it seems to support Webb's hypothesis on the increase of migration away from Hong Kong. However, we may also want to examine if similar data from other major migration destinations for Hong Kongers (i.e. UK, US, Canada, and Australia) show similar results. Another thing we should do is to compare the data in pre-1997 vs 2020 - if they are showing a similar change, we could confidently claim that we are witnessing yet another mass migration happening in Hong Kong.
Another piece of interesting data, which is not discussed in the article is the number of BNO holders applying for LOTR. According to the UK Home Office, the number between 15th Jul to 14th Oct 2020 is 2,116.
Ministry of the Interior National Immigration Agency