Japan’s national Consumer Price Index (CPI) rose 2.1% year on year in September. The article outlines how to assess the impact of higher prices on the “profits” of companies that raised prices, examining changes in average spend per customer, customer numbers and expenses.
The CPI for September 2026 released by the Ministry of Internal Affairs and Communications showed a 2.1% year-on-year rise in the headline index, while the all-items index excluding fresh food also rose 2.1%. The food index excluding fresh food rose 2.9%. The data were released on 23 October 2026 and cover September. These are monthly statistics and do not directly indicate changes in the sales or profits of any specific company.
The article gives an example of how to assess profits after a price increase by combining the growth in average spend per customer with changes in customer numbers. For example, if average spend rises 10% while customer numbers fall 5%, sales increase by approximately 4.5%. It explains that it is necessary to account for expenses, such as food materials, personnel costs and rent, to determine how much remains as profit.
The reasons companies raise prices are not necessarily limited to one factor, and the number of items ordered or the mix of products may also change. The article therefore explains that it is useful to track changes in gross profit, operating profit and expenses in the financial results, in that order. As a method for interpreting monthly data from restaurant and retail companies, it proposes first looking at monthly customer numbers and average spend per customer, followed by gross profit and operating profit.
As additional resources for putting this approach into practice, the article introduces specific educational materials and tools, including a Udemy course, YouTube videos featuring financial-results case studies, a Kindle book and カブヨミ. Finally, it encourages readers to ask at the next financial-results release, “What remained after the price increase?”.