UK PPC Index Methodology

What the index reports

For each of the 19 industries the index covers, two numbers are published per month:

Head-CPC: the volume-weighted average cost-per-click across a fixed basket of 25 high-volume commercial keywords for the vertical. Reflects what advertisers competing on the head of the market pay.
Tail-CPC: a flat average cost-per-click across the same sample. Reflects what advertisers competing further into the long tail pay. The gap between the two is a competitive-squeeze indicator: a wide gap means head competition is bidding the top keywords up faster than the tail; a narrow gap means commodity competition all the way down.

Where the data comes from

The underlying CPC and search-volume figures are drawn from Google Ads Keyword Planner data for the UK market (geo-targeted at United Kingdom, English-language searches). Keyword Planner reports bid-suggestion CPCs that Google publishes to advertisers; it does not report auction-winning CPCs (see "What this data does not show" below). The data is accessed through a licensed third-party API and refreshed monthly.

How industries are selected

Industries are selected from sectors with consistently high commercial activity in UK Google Ads. The data-density criterion is concrete: a vertical is included only if it has at least 40 candidate commercial keywords meeting the volume bar (≥ 100 monthly UK searches, medium-to-high competition, commercial or transactional intent). If a vertical fails the gate in a given refresh cycle, its sub-page is frozen at the last good month rather than estimated, interpolated, or silently removed.

How keywords are selected within each industry

For each industry, 8 to 10 head commercial seed terms are defined (no location modifier, no brand names, no overlap with sibling industries in the index). These seeds are expanded against Google's UK keyword database and filtered to: monthly search volume ≥ 100, competition level in (medium, high), and search intent in (commercial, transactional). The top 25 by monthly search volume become the tracked basket for that industry. The filtered pool below the top 25 is retained for the tail-CPC calculation.

How the head-CPC and tail-CPC are computed

Head-CPC = sum(CPC_i × volume_i) / sum(volume_i) across the 25 tracked keywords. Volume-weighted so a £4 keyword at 50,000 monthly searches counts more than a £25 keyword at 200 searches, which reflects the marketer's actual spend distribution.

Tail-CPC = arithmetic mean of the CPCs across the same 25-keyword sample. A flat average is reported alongside the volume-weighted figure as a check on weighting bias (see "Sample-selection bias" below).

Currency

The index reports cost-per-click values in British Pounds (GBP). The source data is published in USD; values are converted at the monthly-average USD-to-GBP exchange rate for the month in which each value was observed. Exchange rates are sourced from the European Central Bank via the Frankfurter open data API (frankfurter.dev), refreshed alongside each monthly index pull.

Applying month-specific rates means the historical trend reflects actual exchange-rate movements rather than today's rate stretched back across the timeline. A March 2024 reading and a March 2026 reading both convert at the rate that prevailed in that month, so a year-over-year comparison is in real GBP terms.

Downloadable CSV distributions include both cpc_usd (the source value, as published by Google) and cpc_gbp (the converted value, using the month-of-observation rate). Anyone preferring a different conversion methodology can apply it from the raw USD column.

What this data shows

The index reports the bid-suggestion CPC for high-competition commercial keywords in a 25-keyword basket per industry, averaged across the UK Google Ads market. It is the most defensible aggregate available from a publicly-queryable data source. The numbers correlate with what advertisers in these industries actually pay, with the caveats below.

What this data does not show

Actual auction-winning CPC. Google's auction is influenced by Quality Score, ad relevance, landing page experience, and bid strategy. Two advertisers in the same industry bidding on the same keyword can pay different effective CPCs. The index reports the suggested bid that Google's Keyword Planner publishes to advertisers, not the price actually charged after the auction resolves.

Conversion-weighted CPC. A higher CPC in one industry does not mean advertising is less efficient there. Cost per acquisition depends on conversion rate, not CPC. The index is a cost benchmark, not an ROI benchmark.

Brand-keyword CPCs. Brand keywords are excluded by the keyword-selection filter (they have low cost, high volume, and would dominate the volume-weighted mean). The index reports non-brand commercial CPCs only.

Small-sample industries. If an industry cannot clear the 40-candidate data-density gate in a refresh cycle, its sub-page is frozen at the last good month. The index does not synthesise or estimate missing data.

Sample-selection bias

The 25-keyword sample is selected by monthly search volume, and the head-CPC then volume-weights that same sample. The three to five highest-volume keywords in any industry therefore dominate that industry's head-CPC reading. This is intentional: it reflects the experience of advertisers bidding on the head of the market, where the largest cumulative spend sits. But it is not a flat sample-mean of the full long-tail experience. The tail-CPC figure is reported alongside as a check on this bias, and the gap between the two is itself published as a competitive-squeeze indicator.

When the data updates

The index refreshes on the first working day of each month. The last-updated timestamp on the pillar and every sub-page reflects the most recent successful refresh. If a refresh has not completed, the H1 stays pinned to the last good month and the figures shown remain those of that prior month.

How to cite the index

When citing the index in a piece of writing, please use the following format:

Source: Peak Digital UK PPC Index for [Industry], [Month] [Year]. Permalink: https://peakdigital.online/uk-ppc-index/[industry-slug]/

The index is licensed under Creative Commons Attribution 4.0 International. You are free to quote, republish, and adapt the index data for any purpose, including commercial, provided the source is attributed and the permalink linked.