Tag: weighted average

Inflation is measured as the percentage increase in the Consumer Prices Index (CPI) over the previous 12 months. The index is constructed from a basket of goods that is supposed to represent the buying habits of an average UK household. This basket is updated each year as tastes change and as technology moves forward. The basket contains approximately 700 items, with 180,000 individual prices collected each month.

As certain goods become more popular and trends change, the ONS have the responsibility of identifying these changes and updating the basket of goods. The CPI then looks at how the weighted average price of this basket of goods changes from one month to the next. As the CPI gives us the main measure of UK inflation, it is essential that the basket of goods used does represent current consumer demands. If the basket of goods used 20 years ago was still in place, we wouldn’t see thing like mobile phones and ipads being included. This is one sector that has seen significant growth in recent years and the basket of goods has been adapted in response. A new addition to the measure is e-books, which have seen a significant growth in popularity.

However, just as new products have been added to the CPI measure, other goods have been removed. In the most recent update, we’ve seen the removal of champagne and Freeview boxes from the basket of goods. With rapid changes in technological products, such as the ipad, kindle and e-books, products that were new additions only a few years ago are now old news, being replaced by the latest gadgets. Other changes to the basket of goods are less about reflecting consumer trends and more about making certain categories more representative, such as fruits and hot drinks.

So, can the changes in the basket of goods tell us anything about the impact of the recession on buying habits? One notable exclusion from the basket of goods is champagne sold in restaurants and bars. In an economic downturn, you’d expect luxury products to see a decline in consumption and the trend in champagne consumption certainly seems to support the theory. The trends suggest that consumers have instead switched to cheaper alternatives, with things like white rum bought from shops increasing.

Many people may look at the basket of goods and think that it doesn’t reflect what you buy in your average shop. But, the purpose of the CPI is to try to reflect the average consumer and the different items in the basket are given different weightings to give some indication of the amount spent on each good. The articles below look at the changes in the CPI basket of goods and what, if anything, we can take from it.

Inflation basket: E-books added by ONS BBC News (12/3/13)
Inflation basket – what does it say about you? Channel 4 News (12/3/13)
The fizz has fallen flat – champagne cut from inflation basket Independent, Martin Hickman (13/3/13)
E-books added to inflation basket, as champagne dropped The Telegraph, Philip Aldrick (13/3/13)
UK inflation basket: e-books in, champagne out The Guardian, Marking King (13/3/13)
Champagne tipped out of inflation basket Financial Times, Hannah Kuchler (13/3/13)
Champagne out, ebooks in as inflation basket updated Reuters (13/3/13)

Questions

  1. What is inflation and why is it such an important variable?
  2. How is the CPI calculated? Is it different from the RPI?
  3. What impact has technological change had on the basket of goods used to calculate the CPI?
  4. Can you identify any other economic or business trends from the products that are in and out of the CPI basket of goods?
  5. Given the importance of technology and the speed of change, do you think the review of the basket of goods should become more or less frequent?
  6. Has the economic downturn had any effect on the basket of goods used to calculate the CPI?