Reading indicators: seasonally adjusted and original figures have different comparison basesThe same month, but two different things to compare it with
Two statistics released on October 30 each carry figures about the same month but measured against different bases. In the Labour Force Survey the unemployment rate is seasonally adjusted at 2.4% (down 0.1 point from the previous month), while employed persons are given as an original figure of 68.96 million (up 330,000 year on year). The construction starts report gives both a 2.7% decline year on year and a 5.2% decline from the previous month on a seasonally adjusted annual rate basis. Here is how to read the two apart.
Key points
- Original figures are the numbers as collected and still contain seasonal patterns (fiscal year end, summer holidays, year end). That is why comparing with the same month a year earlier is the basic approach
- Seasonally adjusted figures have the seasonal pattern removed statistically, so they can be compared with the previous month. The unemployment rate of 2.4% in the Labour Force Survey is seasonally adjusted and is shown as down 0.1 point from the previous month
- In the same Labour Force Survey, the 68.96 million employed persons and the industry breakdown are original figures, shown against the same month a year earlier (up 330,000)
- An annual rate converts the month's pace into what it would come to over a year. The construction starts report shows a 5.2% decline from the previous month on a seasonally adjusted annual rate basis, which is a different figure from the 2.7% year-on-year decline
- The same applies to your own sales: in a business with a strong seasonal pattern, comparing with the same month a year earlier is safer than comparing with the previous month
What to do in practice
- When quoting figures from published material, always note whether they are seasonally adjusted or original, and whether the comparison is with the previous month or the same month a year earlier
- Add a year-on-year column to your monthly sales trend table (month-on-month alone mixes the seasonal pattern with the underlying trend)
Looking at the statistics released on October 30, figures about the same month of September are mixed together: some say compared with September last year, others say compared with the previous month. The difference is whether the raw numbers are used as they are, or used after the seasonal pattern has been taken out. Ice cream, for example, sells in summer and not in winter. Compared with the previous month, summer always looks like an increase, so some care is needed.
- 1Start with the number just as it was collected (the original figure)
- 2Take out the part that repeats every season by calculation
- 3Compare what is left (the seasonally adjusted figure) with the previous month
Points
- Raw numbers, called original figures, contain the seasonal pattern, so they are compared with the same month a year earlier
- Numbers with the seasonal pattern taken out, called seasonally adjusted figures, can be compared with the previous month
- The September unemployment rate of 2.4% is a seasonally adjusted figure and was 0.1 point lower than the previous month
What the words mean
- original figure
- The number just as it was collected, with the seasonal pattern still in it
- seasonally adjusted figure
- A number with the pattern that repeats every year taken out by calculation, so it can be compared with the previous month
- annual rate
- A number showing what the month's pace would come to if it continued for a year
- Statistics Bureau, Ministry of Internal Affairs and Communications / Ministry of Land, Infrastructure, Transport and Tourism: Statistics Bureau, Labour Force Survey (Basic Aggregates), September 2026 (Reiwa 8): Summary of Results
- Statistics Bureau, Ministry of Internal Affairs and Communications / Ministry of Land, Infrastructure, Transport and Tourism: MLIT, Statistical Survey Report on Construction Starts (September 2026 / Reiwa 8)
Economic news presents published statistics and outlooks. It is not investment solicitation or trading advice. Figures are as of publication and may be revised.
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