1. Main points

  • The Consumer Prices Index including owner occupiers’ housing costs (CPIH) 12-month inflation rate was 2.3% in May 2018, up from 2.2% in April 2018.

  • Rising motor fuel prices produced the largest upward contribution to the change in the rate between April and May 2018.

  • There were also large upward effects from air and sea fares, which rose between April and May this year but fell between the same two months a year ago, influenced by the timing of Easter.

  • Partially offsetting downward effects came from price changes for games, domestic electricity, food and non-alcoholic beverages, and furniture and furnishings.

  • The Consumer Prices Index (CPI) 12-month rate was 2.4% in May 2018, unchanged from April 2018.

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2. Things you need to know about this release

As of 18 April 2018, the prices theme day – which encompasses consumer prices, business prices and house prices – has moved from a Tuesday to a Wednesday. Future release dates and further explanation of the reasons for these changes are available in a separate article.

The National Statistics status of the Consumer Prices Index including owner occupiers’ housing costs (CPIH) was reinstated on 31 July 2017. A letter from the Director General for Regulation to the National Statistician detailed the actions that were taken to meet the requirements as set out in the CPIH assessment report.

We have illustrated our future approach to measuring changing prices and costs faced by consumers and households using three “use cases”, along with how they relate to the measures that we currently publish and those that are under development. Specifically, they refer to the CPIH as our lead measure of inflation based on economic principles; the Household Costs Indices (HCIs, currently under development with preliminary estimates published for the first time on 19 December 2017) as a set of measures to reflect the change in costs as experienced by households; and the Retail Prices Index (RPI) as a legacy measure that is required to meet existing user needs. Shortcomings of the Retail Prices Index as a measure of inflation, released on 8 March 2018, describes the issues with the RPI.

Consumer price inflation is the rate at which the prices of goods and services bought by households rise or fall. It is estimated by using price indices. One way to understand this is to think of a shopping basket containing all the goods and services bought by households. Movements in price indices represent the changing cost of this basket. Consumer price indices – a brief guide gives an overview of the indices and their uses.

The most common approach to measuring inflation is the 12-month inflation rate, which compares prices for the latest month with the same month a year ago. In any given month, the 12-month rate is determined by the balance between upward and downward price movements of the range of goods and services included in the index.

This release also examines how the various types of goods and services contribute to the change in the 12-month inflation rate between the latest two months. The size and direction of these contributions depends on how prices changed between both the latest two months this year and the same two months last year. For example, the price of a product could make an upward contribution to the change in the rate even if it fell, provided that it fell by less than it did between the same two months a year ago. Explaining the contribution to change in the 12-month rate (2013) covers this concept in more detail.

The CPIH is the most comprehensive measure of inflation. It extends the CPI to include a measure of the costs associated with owning, maintaining and living in one’s own home, known as owner occupiers’ housing costs (OOH), along with Council Tax. Both of these are significant expenses for many households and are not included in the CPI.

Aside from including OOH and Council Tax, CPIH is otherwise identical to CPI. This means that, aside from these two components, the factors contributing to the CPI rate are the same as those contributing to the CPIH. For example, if food is reported as increasing the CPIH rate, it is also acting to increase the CPI rate. The size of the contributions for components other than OOH and Council Tax are exaggerated in the CPI compared with the CPIH because they account for a larger proportion of the overall index.

The CPI is produced at the same level of detail as CPIH, in the accompanying dataset and time series.

The Retail Prices Index (RPI) does not meet the required standard for designation as National Statistics. In recognition that it continues to be widely used in contracts, we continue to publish the RPI, its sub-components and RPIX. To view the all-items RPI and 12-month inflation rate and an at-a-glance comparison with other measures, please see the time series section of the inflation and price indices area of our website. The accompanying dataset and time series provide more detailed information.

The figures in this publication use data collected on or around 15 May 2018.

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3. CPIH 12-month rate up slightly in May 2018

The Consumer Prices Index including owner occupiers’ housing costs (CPIH) 12-month rate was 2.3% in May 2018, up from 2.2% in April 2018. The rate had fallen steadily from a recent high of 2.8% in autumn 2017 to 2.2% in April 2018, which was influenced by the timing of Easter. It has since risen slightly into May, in part due to the unwinding of the Easter effect. More information on this can be found in the Prices economic commentary for June 2018.

Figure 1 compares the 12-month inflation rates for CPIH and CPI, along with the rate for the owner occupiers’ housing costs (OOH) component of CPIH. Given that OOH accounts for around 17% of CPIH, it is the main driver for differences between the CPIH and CPI inflation rates.

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4. Upward effect on the CPIH inflation rate from most broad categories of goods and services

Figure 2 shows that price movements for most of the broad categories of goods and services had an upward effect on the Consumer Prices Index including owner occupiers’ housing costs (CPIH) 12-month rate in May 2018. The exception was miscellaneous goods and services, which had a negligible effect.

The largest upward contribution to the CPIH 12-month rate came from transport, where prices rose by 4.6% in the year to May 2018 leading to a contribution of 0.58 percentage points to the CPIH 12-month rate. The May 2018 rate for transport is the highest since April 2017 when it was 6.2%. Housing and household services continues to make a large upward contribution (of 0.47 percentage points in May 2018), though for the first time since April 2017, it is not the largest contribution.

Figure 3 shows the extent to which the different categories of goods and services have contributed to the overall CPIH 12-month rate over the last two years. In particular, transport, and food and non-alcoholic beverages prices have been important factors in driving the changes in the rate. As the overall CPIH rate began to level off from April 2017, the contribution from food and non-alcoholic beverages continued to increase, being offset by a fall in the contribution from transport, particularly motor fuels.

During 2018, the contributions from most of the categories have fallen back, leading to a fall in the 12-month rate. This was true of transport between January and April. However, its contribution has almost doubled between April and May, rising from 0.30 percentage points in April to 0.58 percentage points in May.

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5. Transport contributes most to the change in the rate between April and May 2018

Figure 4 shows how each of the main groups of goods and services contributed to the change in the Consumer Prices Index including owner occupiers’ housing costs (CPIH) 12-month rate between April and May 2018. The corresponding figures for the Consumer Prices Index (CPI) can be found in column F of Table 26 in the Consumer price inflation dataset.

The only large upward contribution to the change in the CPIH rate came from transport, principally from motor fuels, air fares and sea fares. Petrol prices rose by 4.6 pence per litre between April and May 2018 to stand at 125.3 pence per litre in May, the highest average price since October 2014. This compares with a 1.0 pence per litre fall between the same two months of 2017 to stand at 116.4 pence per litre in May 2017. Similarly, diesel prices rose by 4.7 pence per litre between April and May 2018 compared with a 1.6 pence per litre fall between the same two months a year ago. These recent rises reflect increases in the price of crude oil.

Within the broad transport group, there were also large upward effects from air and sea fares. Fares in both categories rose between April and May this year but fell between the same two months a year ago. The timing of Easter in the middle of April 2017 contributed to relatively high fares in that month with subsequent price falls into May 2017. This year, Easter fell at the beginning of April before the price collection period leading to relatively lower fares being observed and subsequent price rises into May.

The largest, partially offsetting downward effect came from a range of recreational and cultural goods and services, where prices, overall, rose by 0.1% between April and May this year compared with a larger rise of 0.9% between the same two months a year ago. The main effect came from games, toys and hobbies, where prices fell this year but rose a year ago, particularly for computer games. Prices for these games are heavily dependent on the composition of bestseller charts, often resulting in large overall price changes from month to month.

Housing and household services also had a large downward effect, with domestic electricity prices rising by 0.1% between April and May 2018 compared with 4.0% between the same two months a year ago.

The final large downward contribution came from food and non-alcoholic beverages. This was from a range of food products, with the largest single effect coming from sugar, jam, syrups, chocolate and confectionery, where prices fell this year but rose a year ago. Partially offsetting this was a small upward effect from vegetables, where prices rose this year but fell a year ago.

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8. Quality and methodology

The Consumer Price Inflation Quality and Methodology Information report contains important information on:

  • the strengths and limitations of the data and how it compares with related data

  • users and uses of the data

  • how the output was created

  • the quality of the output including the accuracy of the data

The Consumer Price Indices Technical Manual covers the concepts and methodologies underpinning the indices in more detail.

The CPIH Compendium provides a comprehensive source of information on the Consumer Prices Index including owner occupiers’ housing costs (CPIH), with a focus on the approach to measuring owner occupiers’ housing costs (OOH).

The Consumer price inflation basket of goods and services: 2018 article details the annual review process for the items making up the inflation basket used to calculate the UK consumer price inflation indices and describes the changes in the latest year.

Consumer price inflation, updating weights: 2018 describes the latest changes to the relative weights of items in the inflation basket to ensure they remain representative of current consumer spending patterns.

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