2d:null 2e:["$","title",null,{"children":"Averaging regional growth can reverse the answer | Matt Lenzie | Observable"}] 33:T48e,# Averaging regional growth can reverse the answer Matt Lenzie | Commercial Mortgages Broker research | 7 October 2026 In H1 2026, the [London and South East report](https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/london-and-south-east) records 2,520 classified commercial-property charges, up from 2,404. The [Wales report](https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/wales) records 373, down from 406. Together, the two areas rose from **2,810 to 2,893 charges: +3.0%**. Yet the simple average of their two growth rates is **-1.7%**. Both calculations are valid. They answer different questions. The first measures the change in the combined count. The second gives each regional percentage equal influence, despite the difference in starting counts. Confusing them can turn an increase into a decline. This deliberately selected two-area example makes the distinction visible; it is not a national estimate. Use the calculator to switch to all seven report groups or choose your own subset. These are classified Companies House charge instruments, not loan amounts, approvals or unique borrowers. 34:T2976,const regionalChargeData = [ { "area": "london-and-south-east", "name": "London and South East", "previous": 2404, "current": 2520, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/london-and-south-east", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/london-and-south-east.csv", "sha256": "20d1e6387e8e3ae46bbb9f7bea20bc136a9a1d2412a1cf8d1aa8fd2e0f688441" }, { "area": "midlands", "name": "Midlands", "previous": 1203, "current": 1290, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/midlands", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/midlands.csv", "sha256": "e3542164245dcf23645a1d5f15a1165fe83ec6b6a5a854a8c1a10ed552f87cc2" }, { "area": "north-west", "name": "North West", "previous": 1125, "current": 1032, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/north-west", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/north-west.csv", "sha256": "bd6a16353162c5a3337148f6756ad12dbb9110d94129554d7d8b55e025ae284d" }, { "area": "north-east-and-yorkshire", "name": "North East and Yorkshire", "previous": 962, "current": 992, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/north-east-and-yorkshire", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/north-east-and-yorkshire.csv", "sha256": "45e64f8faeb7801f8a5b4ba6720f7866d6abde5075690e8069d5fd321f12ea8a" }, { "area": "south-west", "name": "South West", "previous": 815, "current": 840, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/south-west", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/south-west.csv", "sha256": "b25cf16ae7397e05543ff1392d8db8d4003d6932ff861842fa961f0938a3063c" }, { "area": "east-of-england", "name": "East of England", "previous": 705, "current": 709, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/east-of-england", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/east-of-england.csv", "sha256": "a8cef7943888113d39b58ea4d8acb11641ef019a3c037ecb461c342aa0ea409a" }, { "area": "wales", "name": "Wales", "previous": 406, "current": 373, "report": "https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3/wales", "csv": "https://commercialmortgagesbroker.co.uk/data/commercial-reports/2026-q3/wales.csv", "sha256": "09e5b93c3d9f11052e93625535b122f7e52b9532c4eeeeb2a9171c65519b6b3e" } ]; function regionalWeightExplorer(data) { const root=document.createElement('section'); root.className='cmb-weights'; root.innerHTML=`

Choose report groups

${data.map(d=>`${d.name}`).join('')}

H1 2025 versus H1 2026. Classified Companies House charge instruments. Source: Commercial Mortgages Broker, Jan-Sep 2026 edition; charge snapshot 1 October. Groups are selected for illustration, not matched by size. No lending-value estimate.

`; const fmt=n=>n.toLocaleString('en-GB'),signed=n=>(n>0?'+':'')+fmt(n),pct=n=>(n>0?'+':'')+n.toFixed(1)+'%'; const inputs=[...root.querySelectorAll('input')];let selected=[]; function render(){ selected=data.filter(d=>inputs.find(i=>i.value===d.area).checked); const result=root.querySelector('.results'),download=root.querySelector('.download'); download.disabled=!selected.length; if(!selected.length){result.innerHTML='

Choose at least one report group to calculate a comparison. No areas selected; no growth rate is defined.

';return;} const a=selected.reduce((s,d)=>s+d.previous,0),b=selected.reduce((s,d)=>s+d.current,0); const weighted=100*(b-a)/a,equal=selected.reduce((s,d)=>s+100*(d.current-d.previous)/d.previous,0)/selected.length; result.innerHTML=`

${selected.length===7?'All seven groups: England and Wales':'Selected subset: '+selected.length+' of seven groups'}. ${selected.map(d=>d.name).join('; ')}.

Growth in combined charge count${pct(weighted)}${fmt(a)} in 2025 → ${fmt(b)} in 2026
${signed(b-a)} charges; weighted by 2025 counts.

Equal-weight mean of regional rates${pct(equal)}${selected.length===1?'The selected group has':'Each of the '+selected.length+' selected groups has'} a ${(100/selected.length).toFixed(1)}% weight.
${selected.length===1?'With one group, the two results coincide.':'Equal regional influence, regardless of starting count.'}

The weights behind the combined result

Each bar shows its share of the selected 2025 charge count, on the same 0% to 100% scale. These are count shares, not shares of lending value.

${selected.map(d=>`

${d.name}${(100*d.previous/a).toFixed(1)}%

`).join('')}

Check the counts and source reports

Rates use unrounded counts. Scroll the table horizontally on narrow screens.

${selected.map(d=>``).join('')}

H1 charge counts for selected groups
Report group	2025	2026	Change	Growth	Source
${d.name}	${fmt(d.previous)}	${fmt(d.current)}	${signed(d.current-d.previous)}	${pct(100*(d.current-d.previous)/d.previous)}	CSV
${selected.length===7?'England and Wales':'Selected subset total'}	${fmt(a)}	${fmt(b)}	${signed(b-a)}	${pct(weighted)}	Combined count

Combined calculation: 100 × (${fmt(b)} − ${fmt(a)}) ÷ ${fmt(a)} = ${pct(weighted)}. Equal-weight calculation: add the ${selected.length} unrounded regional rates and divide by ${selected.length}.

`; } inputs.forEach(i=>i.addEventListener('change',render)); root.querySelectorAll('[data-preset]').forEach(btn=>btn.addEventListener('click',()=>{inputs.forEach(i=>i.checked=btn.dataset.preset==='all'||(btn.dataset.preset==='pair'&&['london-and-south-east','wales'].includes(i.value)));render();})); root.querySelector('.download').addEventListener('click',()=>{ const total=selected.reduce((s,d)=>s+d.previous,0); const keys=['report_group','period','charges_2025','charges_2026','difference','growth_pct','prior_count_weight_pct','equal_weight_pct','report_url','source_csv_url']; const rows=selected.map(d=>[d.name,'H1',d.previous,d.current,d.current-d.previous,100*(d.current-d.previous)/d.previous,100*d.previous/total,100/selected.length,d.report,d.csv]); const csv=[keys,...rows].map(row=>row.map(v=>'"'+String(v).replaceAll('"','""')+'"').join(',')).join('\n'); const url=URL.createObjectURL(new Blob([csv],{type:'text/csv;charset=utf-8'}));const link=document.createElement('a');link.href=url;link.download='cmb-h1-regional-weighting-selection.csv';link.click();setTimeout(()=>URL.revokeObjectURL(url),1000); });render();return root; } display(regionalWeightExplorer(regionalChargeData)); 35:Te49,## The starting count supplies the weight London and South East accounts for **85.6%** of the pair's 2025 count; Wales accounts for **14.4%**. Weight each growth rate by those starting shares and the result is +3.0%, matching the change in the combined count. Giving both rates a 50% weight instead produces -1.7%. The arithmetic is easiest to reproduce from counts: London and South East adds 116 charges, Wales subtracts 33, and the combined increase of 83 is divided by the combined 2025 base of 2,810. Use full-precision rates when checking the weighted calculation; displayed percentages are rounded. ## What happens across all seven groups? Select **All seven groups** above. The combined count rises from **7,620 to 7,756**, or **1.8%**, matching [Commercial Mortgages Broker's England and Wales report](https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3). The equally weighted mean of the seven regional rates is **0.3%**. Here the methods agree on direction but differ substantially in magnitude. That is a useful competing check: averaging regional rates does not always reverse the sign. The two-area example exposes a possibility, not a rule that regional averages are inherently misleading. An equal-weight mean is meaningful if the question is explicitly about the average rate across these seven report groups. It is unsuitable as a substitute for growth in their combined charge count. The groups also differ in their geographic scope. London and South East is a combined reporting area, while Wales is one national area within this England and Wales dataset. Equal weights do not make the units comparable in population, property stock or commercial activity. ## A practical check before quoting a market percentage For a combined-count headline, add the current counts, add the same areas' prior-period counts, then calculate **100 × (current total − prior total) ÷ prior total**. For an average-area headline, name the weighting rule and the exact areas. A selected subset must remain labelled as a subset. Do not weight these growth rates by 2026 counts: the identity uses the 2025 denominator from which each rate was calculated. And do not treat either result as a measure of lending value. Multiple charge instruments can relate to one borrower or financing arrangement; the public aggregates cannot establish the amount advanced. ## Sources and reproduction The calculator contains seven H1 2025/H1 2026 regional comparisons from CMB's Jan-Sep 2026 report edition. H1 is January to June; provisional Q3 is excluded. The reported charge snapshot is 1 October 2026. Public CSVs were rechecked on 7 October and matched the previously frozen source bytes. Every region's report and CSV is linked directly in the interactive table. The [existing public research package](https://github.com/mattylll/cmb-commercial-property-charges-2026) provides the wider 52-row comparison dataset and source manifest. The [report methodology](https://commercialmortgagesbroker.co.uk/research/commercial-property/2026-q3#methodology) describes the classification context. Reproduction here checks published aggregates and arithmetic, not individual Companies House filings or the upstream classification process. Later filings and revisions can change the source series. Download the selected rows to check the two totals and weighting yourself. The notebook's code is visible through Observable. Commercial Mortgages Broker is a brokerage; this is an explanatory adaptation of its existing research, not independent corroboration or a new study. No borrower identities or private lending records are included. 36:[] 31:{"id":"63be7762444077a9","slug":"averaging-regional-growth-can-reverse-the-answer","title":"Averaging regional growth can reverse the answer","thumbnail":"9d32173288fc8cde0f62248ad0838c2a0167c5c1bf3bf6497a28c65b389edb24","access_level":"public","create_time":"$D2026-10-07T18:44:31.369Z","update_time":"$D2026-10-07T18:47:54.493Z","view_time":null,"first_public_time":"$D2026-10-07T18:49:02.719Z","has_unpublished_edits":null,"fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"ea2de9ba2c0a2ed6","login":"matt-lenzie","name":"Matt Lenzie","avatar_url":null,"tier":"free_2026","bio":""},"version":15,"publish_version":15,"role":null,"authored":false,"authors":[{"type":"individual","id":"2a28c9706791cd4f","login":"matt-lenzie","name":"Matt Lenzie","avatar_url":null,"tier":null,"bio":""}],"members":[{"type":"team","id":"ea2de9ba2c0a2ed6","login":"matt-lenzie","name":"Matt Lenzie","avatar_url":null,"tier":"free_2026","role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":null,"type":"notebook","body":{"titling":"auto","title":"Averaging regional growth can reverse the answer","cells":[{"id":1,"value":"$33","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":2,"value":"$34","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":4,"value":"$35","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W36","stdlib":"2"}} 32:"$31:body"