Three Sources, One Wrong Claim
A student is given three sources. Source 1: a line graph showing foreign visitors to Japan rising from 8.4 million in 2012 to 31.9 million in 2019, falling to 0.4 million in 2021, and recovering to 25.1 million in 2023. Source 2: a table of foreign workers in Japan rising from 0.68 million in 2012 to 2.05 million in 2023, with the largest increases in food service, care, and construction. Source 3: a map of prefectural population change 2010–2020 showing that only Tokyo, Kanagawa, Saitama, Chiba, Aichi, and Fukuoka gained population, while 41 prefectures lost. The student writes: 'The growth in foreign visitors and workers explains why rural prefectures stopped losing population after 2015.' The student also calculates that visitors grew 278% from 2012 to 2019.
1. Identify two errors in the student's reasoning and explain how the sources contradict the claim.
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Error 1: aggregation error-national visitor and worker totals cannot show prefectural population change; Source 3 shows 41 prefectures lost population 2010–2020, including after 2015. Error 2: timing and location-visitor growth is concentrated in Tokyo–Kyoto–Osaka routes and foreign workers in food service, care, and construction, which are urban or peri-urban; the table has no prefecture breakdown. A third problem: the student's 278% ignores the 2020–21 collapse; 2023 visitors were still below 2019. The sources contradict the claim rather than support it.
2. Calculate the percentage change in foreign workers from 2012 to 2023, and explain what the result does and does not show.
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2.05/0.68 = 3.01, so the change is about +201% (201.5%). It shows the stock of foreign workers roughly tripled; it does not show where they live, whether they stayed, or whether their presence caused population change. A percentage change from a small base can look large; the absolute increase is 1.37 million.
3. Design one additional piece of evidence that would make the student's claim testable, and state what result would support it.
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Evidence: prefecture-level data on the foreign resident share in 2015 and population change 2015–2020, with controls for age structure and employment. If the claim is right, prefectures with larger foreign-resident increases should show smaller population losses. A result of no association, or association only in the six gaining prefectures, would refute it.