Beyond the average: patterns in UK price data at the micro level

Lennart Brandt, Natalie Burr and Krisztian Gado

The Financial institution of England has a 2% annual inflation charge goal within the ONS’ client costs index. However its 700 merchandise classes, we discover that only a few costs ever change by 2%. Actually, on a month-on-month foundation, solely about one fifth of costs change in any respect. As an alternative, we observe what economists name ‘sticky costs’: the value of an merchandise will stay fastened for an prolonged period of time after which regulate in a single massive step. We doc the time-varying nature of stickiness by wanting on the share of value adjustments and their distribution within the UK microdata. We discover a seen discontinuity in price-setting within the first quarter of 2022, which has solely partially unwound.

Principle of sticky costs and associated literature

Understanding price-setting dynamics is crucial for central banks. Most structural fashions within the literature use a type of time-dependent pricing, underneath which corporations maintain costs the identical for fastened quantities of time (Taylor (1980)), or for random quantities of time such that there’s uncertainty in regards to the exact size of the value spell (Calvo (1983)). One other manner of modelling sticky costs emphasises that corporations won’t simply have a look at the time that has handed since they final adjusted its value, but in addition at how far their value is from some desired value degree. That is known as state-dependent pricing. Macroeconomic fashions don’t usually permit for time-variation within the diploma of stickiness or switching between pricing methods. Just lately, nonetheless, corporations within the Determination Maker Panel inform us that they’ve moved more and more away from time-dependent in direction of state-dependent pricing. On this case, when there’s a massive shock affecting many corporations, the shock results in an elevated frequency of value adjustments and so extra quick pass-through to total inflation.

In an effort to higher perceive the pricing behaviour of corporations in occasions of huge inflationary shocks, we discover the pricing dynamics on the micro degree utilizing CPI microdata revealed by the ONS. We’re in fact not the one ones who’ve been concerned with this kind of knowledge. Financial institution authors have been utilizing this knowledge set for a lot of years. For instance, Bunn and Ellis (2011) doc stylised information about pricing behaviour from the UK microdata and the August 2020 Financial Coverage Report used CPI microdata to tell coverage. Elsewhere, Karadi et al (2020) use US microdata to analyse corporations’ price-setting in response to adjustments in credit score circumstances and financial coverage. Nakamura et al (2018) analyse the societal price of excessive inflation utilizing microdata from the Seventies and Eighties, and Montag and Villar (2023) analyse the impact of extra frequent price-changes on combination inflation throughout Covid. Relatedly, Davies (2021) finds that the distinction between the share of value rises and value cuts within the UK microdata is expounded to combination inflation, specializing in price-setting in the course of the pandemic. And eventually, authors of the FT’s Alphaville weblog have additionally been wanting into these knowledge (see right here and right here).

The info

The microdata spanning from 1996 till September 2023 is publicly accessible and up to date month-to-month after every CPI launch. It accommodates the month-to-month value quote knowledge underpinning the ONS’ CPI sequence for over 700 objects with identifiers on the store, store sort, and area ranges. We clear the info which works out to about 30 million observations. When figuring out a value change within the knowledge, which is in the end what issues for inflation, we attempt to be as exact as attainable with reference to the product and the timing of the change. To that finish we solely depend the change if we discover the identical merchandise, in the identical area, in the identical store, in two precisely neighbouring months. For instance, if a bag of potatoes price £2 in January and £3 in March however was not recorded in February, slightly than imputing a value we discard the statement since we can’t be positive wherein month the change truly occurred.

Stylised information from the microdata

A quick have a look at the info lets us set up some stylised information. Chart 1 exhibits a decomposition of those month-on-month value actions over all objects within the knowledge set. 4 key observations stand out:

Costs rise and fall on a regular basis, however the overwhelming majority of costs don’t change between months. In any given month, on common since 1996, round 80% of costs stay unchanged relative to the earlier month (blue line).

The share of costs rising (in inexperienced) has elevated notably since 2021 to an extent that has not occurred in earlier inflationary episodes within the pattern (excluding VAT adjustments).

The share of costs falling (in purple) has fallen considerably however stays steady since 2021, relative to historic common. The primary margin of adjustment has been within the share of value will increase.

However, in current months, whereas the share of costs rising has tapered off, it stays elevated relative to its historic common. 

Chart 1: Decomposition of value actions month-on-month

Notes: The share of costs rising and falling replicate month-on-month adjustments. Shares are seasonally adjusted utilizing the R bundle seasonal. Spikes in 2008, 2010 and 2011 are a consequence of UK VAT adjustments (17.5% to fifteen% in 2008, enhance to 17.5% in 2010 and enhance to twenty% in 2011). The gray shaded space covers the time between March 2020 and July 2021 when the economic system (and knowledge assortment) was most affected by the Covid pandemic. Dashed strains present the 2011–19 averages. Newest statement: September 2023.

Sources: ONS and authors’ calculations.

To be clear, this chart is just not saying that 80% of merchandise by no means change costs. If the value of an merchandise remained fixed between December and January, and rose between January and February, it might transfer from the blue into the inexperienced class throughout this era. Equally, it might fall out of the inexperienced, into the blue or purple, if from February to March the value once more remained fixed, or fell, respectively.

So, maybe surprisingly, this chart exhibits that month-to-month value dynamics within the economic system are pushed by solely a comparatively small fraction of roughly 20% of all items and providers within the consumption basket. Additionally, we see that in the latest episode, the shift into rising costs has been largely out of the ‘no change’ class. Therefore, fewer costs are staying fastened, and extra are rising. It’s value noting that the current up-tick within the shares of costs rising is just matched traditionally by these attributable to VAT adjustments in 2008, 2010 and 2011, which nonetheless seem as one-off value spikes slightly than a persistently greater share of value rises, as in 2022.

If it’s a minority of complete merchandise whose value adjustments, it is very important take a more in-depth look. Chart 2 exhibits the distribution of costs adjustments from 2019 by quarter (truncated at zero to exclude no-change observations). Consistent with the rise within the inexperienced line in Chart 1, we observe that over 2021 and 2022 plenty of mass moved into the correct facet of the distribution, that’s the share of value will increase, with the share of value decreases being comparatively steady.

Chart 2: Evolution of the distribution of value adjustments by quarter 2019–23

Notes: The share of costs that didn’t change is excluded from these densities. The truncated densities are estimated in R by way of the Bounded Density Estimation bundle utilizing the boundary kernel estimator. Darker colors correspond to quarters wherein year-on-year CPI inflation was comparatively excessive, lighter colors to quarters wherein it was low. Every distribution represents month-on-month adjustments inside the similar quarter. Newest statement: 2023 Q3.

Sources: ONS and authors’ calculations.

A observe on the chart: the distribution of value adjustments, when combination inflation is at or shut to focus on, is roughly symmetric in logarithms. On this scale, a doubling (+100%) is equally distant from zero as a halving of the value (-50%). As a consequence of gross sales, the doubling and halving of costs truly occurs recurrently within the knowledge, which explains the bunching round these factors. Whereas these could also be a supply of seasonality within the knowledge, which can obscure the underlying dynamics, we don’t imagine they’re vital for the general form of the distribution which we present right here.

In Chart 3, we zoom in on a few these densities to higher see variations of their form. They’re the densities corresponding to cost adjustments within the third quarter of 2022 and 2023 alongside a median density over the pre-Covid interval.

Chart 3: Comparability of densities from 2022 and 2023 towards a pre-Covid common

Notes: The share of costs that didn’t change is excluded from these densities. The truncated densities are estimated in R by way of the Bounded Density Estimation bundle utilizing the boundary kernel estimator. To check densities throughout time, they’re normalised to sum to the common share of costs falling and rising respectively inside the quarter. The yellow line exhibits the pointwise common density over the third quarters of the years 2011–19.

Sources: ONS and authors’ calculations.

We are able to see how, in comparison with this historic common – which we use as a stand-in for pricing behaviour when inflation was near the two% inflation goal – 2022 noticed an enormous variety of costs enhance whereas there was little change within the behaviour of the decrease a part of the distribution. Within the newest knowledge, this mass of will increase has begun to subside, and, on the similar time, there’s a rising variety of costs outright falling on the month. Nevertheless, the modal value enhance (that’s, probably the most possible) remains to be elevated at about 6%, in comparison with roughly 3% on common throughout 2011–19).

Conclusion

To summarise, wanting on the micro degree of value adjustments, we discover a seen discontinuity in price-setting within the first quarter of 2022. A wide range of components, corresponding to the massive rise in vitality costs in early 2022, in addition to supply-chain points following Covid lockdowns, doubtless contributed to this important change in price-setting dynamics within the UK (relative to any current historic precedent at the least). On the micro degree, corporations’ pricing selections led to the emergence of a big rebalancing within the distribution of value adjustments. Out of the blue, extra costs for a lot of totally different merchandise have been rising on the similar time. In comparison with the accessible historical past for these knowledge, the current interval is exclusive. Extra analysis will likely be wanted on the causes of this marked shift within the distribution of value adjustments, each at a micro and at a macro degree.

Within the very newest knowledge, there’s some proof that the distribution of value adjustments has certainly begun to return within the course of its historic common, although it’s too quickly to ascertain a pattern.

Lennart Brandt and Natalie Burr work within the Financial institution’s Exterior MPC Unit, and Krisztian Gado is a PhD candidate at Brandeis College.

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