Four Years, Four Numbers
A class in Kanazawa is studying how transport changes a city. In March 2015 the Hokuriku Shinkansen opened between Nagano and Kanazawa; in March 2024 it was extended to Tsuruga. The table gives simplified classroom figures for the city.
| Year | Overnight visitors (万人) | Hotel rooms | Foreign visitors' share |
|---|---|---|---|
| 2014 | 700 | 11,000 | 5% |
| 2019 | 1,000 | 15,500 | 15% |
| 2020 | 500 | 15,000 | 1% |
| 2023 | 850 | 15,200 | 6% |
Hotel occupancy in the city centre is about 80% in spring and autumn but under 50% in January and February. The Noto region has many small inns but few large hotels. A classmate writes in a report: 'The Shinkansen increased Kanazawa's visitors by 43%, so the city should build more hotels.' Another answers: 'Correlation is not causation.'
1. Calculate the percentage change from 2014 to 2019 and from 2019 to 2023. What does the comparison show, and what does it hide?
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Calculations.
- 2014 to 2019: (1,000 - 700) / 700 = 0.429, so about +43%.
- 2019 to 2023: (850 - 1,000) / 1,000 = -0.15, so about -15%.
- 2014 to 2023: (850 - 700) / 700 = about +21%.
What it shows. The large rise came in the years just before and after the Shinkansen opened, and the 2020 fall coincides with the pandemic year. By 2023 the city was still 15% below 2019 but 21% above 2014.
What it hides. Hotel rooms also grew from 11,000 to 15,500 by 2019, about +41%, almost the same rate as visitors. That means rooms and visitors rose together, which is consistent with the Shinkansen helping, but also consistent with both being driven by something else, such as the inbound travel boom: the foreign share tripled from 5% to 15% over the same years. With four data points, a single yearly percentage cannot separate these explanations.
2. A classmate claims 'the Shinkansen increased visitors by 43%'. Give one reason this conclusion is too strong and name one piece of evidence that would help test it.
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Why it is too strong. The 43% is measured between two single years, 2014 and 2019, and the Shinkansen is only one of many things that changed in that window: exchange rates, visa rules, low-cost flights, and a general rise in travel from East Asia. The foreign share rising from 5% to 15% shows that at least one of those other factors was moving strongly. A correlation between opening a line and more visitors does not by itself show the line caused the increase.
Evidence that would help.
- Monthly data. If the Shinkansen caused the rise, arrivals should step up sharply in the months after March 2015, not drift upward smoothly from 2012.
- A comparison city. A city of similar size and attractions that did not receive a Shinkansen, tracked over the same years, works as a control.
- A visitor survey. Asking how visitors travelled shows directly whether the new line carried them, and how many came because of it rather than despite it.
The class should also ask for the mechanism: travel time from Tokyo fell by a known amount, so the day-trip range expanded. A plausible mechanism makes the causal claim stronger than a bare correlation.
3. Using the table and the occupancy figures, advise the mayor on whether to build more hotels in the city centre or to spread visitors into Noto. State one counter-argument your advice must answer.
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Advice: spread the visitors, and do not build first.
The reasoning runs in three steps.
- Capacity is nearly fixed. Rooms barely moved from 15,500 in 2019 to 15,200 in 2023, while visitors in 2023 were already back to 850 万人. City-centre occupancy is about 80% in spring and autumn, so at peak the city is close to full.
- The empty season is the real problem. Occupancy under 50% in January and February means new rooms would be empty for two months. Building adds cost that must be paid all year to serve a peak that lasts a few weeks.
- Noto already has beds. Small inns exist, so directing visitors there raises capacity without new construction and spreads income to a region that needs it - especially after the 2024 earthquake.
The counter-argument to answer. Noto's roads and rail links are weaker, and after the earthquake some inns are closed and travellers may avoid the area. If access and safety cannot be guaranteed, a dispersal policy will fail. The answer is a staged one: promote Noto day trips and short stays on the restored routes first, measure take-up by season, and build city hotels only if peak occupancy stays near 80% with Noto included.