Space retention rate measures the show floor your renewals actually hold

The floorplan lead for a machinery show asked for one number in November and could not get it out of the renewal report. How many square metres do I have to sell before we open?

The renewal report said retention was 73.6 per cent. That answer is useless to her, because she does not sell companies. She sells floor, and 73.6 per cent of the companies could be holding anywhere between half and nearly all of the hall. A space retention rate is the version of the measure that answers her, and it has a denominator decision of its own to settle first.

Which denominator does the rate use?

Retention measured in area has the same denominator problem as every other retention measure, and it produces a wider spread than most people expect.

The first version divides the space that returning exhibitors hold at edition N plus 1 by the space those same exhibitors held at edition N. It is a statement about the returning cohort: of the floor held by companies that came back, how much did they come back with. This is the number most organisers mean when they say space retention.

The second version divides the same numerator by the total space sold at edition N. It is a statement about the hall: of the floor we sold last time, how much is held by a renewal this time. Everything not in that fraction is floor the sales team has to fill again.

Both are defensible and they answer different people's questions. Publish one without saying which and the two halves of the building will argue for a year.

The arithmetic on one hall

288 exhibiting companies at edition N holding 14,600 net square metres between them, which is about 157,000 net square feet if your board reads in feet.

212 of those companies return at edition N plus 1, so logo retention is 212 over 288, which is 73.6 per cent.

Those 212 companies held 12,880 square metres at edition N, so the 76 companies that left held 1,720. The leavers averaged 22.6 square metres each. The returners averaged 60.8. Your departing exhibitors were roughly a third the size of your surviving ones, which is the composition fact that everything else here follows from.

At edition N plus 1 the 212 returning companies contract 12,410 square metres.

Space retention on the returner denominator is 12,410 over 12,880, which is 96.4 per cent. Space retention on the hall denominator is 12,410 over 14,600, which is 85.0 per cent.

So one cohort, one pair of editions, three legitimate numbers: 73.6 per cent of companies, 96.4 per cent of the returners' floor, 85.0 per cent of the hall. The spread between the first and the last is more than eleven points, and the spread between the first and the second is nearly twenty three.

I would publish 85.0 as the headline and keep 96.4 as a diagnostic. The hall version is the one that converts directly into work: 14,600 minus 12,410 is 2,190 square metres to resell, which is 15.0 per cent of the floor, and at an average new exhibitor taking 24 square metres that is about 91 companies the new business team has to sign. The returner version flatters. A show can post 96.4 per cent space retention while a quarter of its floor sits empty, because the denominator quietly excludes everybody who left.

Who released floor and who absorbed it

The 470 square metre difference inside the returning cohort is a net figure, and netting hides the interesting part.

Of the 212 returning companies, 90 took exactly the same space, 5,100 square metres on both sides. 64 grew, from 4,180 to 4,990, adding 810. 58 shrank, from 3,600 to 2,320, releasing 1,280. The three groups sum to 212 companies and to 12,880 square metres of base year space, which is the check to run before anyone quotes the result.

So 58 accounts that renewed released 1,280 square metres, and 64 accounts that renewed absorbed 810 of it. The shrinkers cut an average of 22.1 square metres each from an average base of 62.1, a reduction of 35.6 per cent on themselves. Every one of those 58 companies appears as a successful renewal in the count.

Expressed against the 14,600 square metre hall, the whole movement reads as three numbers. Departures took 11.8 points. Shrinkage inside the returning book took another 8.8. Growth inside the returning book gave back 5.5. Start at 100 and you arrive at 85.0.

Shrinkage taking 8.8 points against departures taking 11.8 is the part that surprises people. Nearly as much floor came out of accounts that renewed as out of accounts that left, and none of it appears in any measure built on a count of companies. If your renewal programme only has a workflow for lapses, it is addressing slightly more than half of the problem it thinks it owns, and renewal intelligence built on presence alone will never surface the other half.

What can a count of companies not tell the floorplan team?

Hold logo retention at exactly 73.6 per cent and change only the size of the companies that left.

If the 76 departing companies had averaged 60 square metres each, the size of the returning cohort, they would have taken 4,560 square metres with them and left the returners holding 10,040. Keep the returners behaving exactly as they did, at 96.4 per cent, and they rebook 9,679. The hall version of space retention drops from 85.0 to 66.3 per cent, the resell task more than doubles from 2,190 square metres to 4,921, and the count of companies does not move by a single account.

That is the whole argument for the measure. A show can lose a quarter of its exhibitors and 15 per cent of its floor, which is a tidy year, or lose a tenth of its exhibitors and 30 per cent of its floor, which is an emergency, and the retention rate on the board slide reads better in the second case.

Area also survives things that revenue does not. A rate card increase moves revenue retention without a square metre changing hands, so a show that put prices up 6 per cent will post a revenue retention figure contaminated by the pricing decision. Square metres are immune to that, which makes area the cleaner measure of what exhibitors actually did and the better one to compare across editions where pricing moved. Revenue weighted retention has its own job and answers to finance rather than to the floorplan.

The industry measures itself in area

There is a practical reason to hold a space retention rate alongside the count, which is that the published comparators are in area.

The CEIR Index, produced by the Center for Exhibition Industry Research, the research division of IAEE, together with Tourism Economics, an Oxford Economics company, measures year on year change in four things: net square feet of exhibit space sold, professional attendance, the number of exhibiting companies, and gross revenue. Its 2026 report forecasts the CEIR Total Index growing 2.1 per cent in 2026. A show that only tracks retention in companies has nothing to put next to the first of those four metrics.

The one industry figure I know of that reports both sides of this on the same survey is the 2015 Benchmarks and Trends in Exhibit and Sponsorship Sales study, run jointly by Exhibit Surveys, Lippman Connects and Trade Show Executive, whose 206 respondents in exhibit and sponsorship sales put year to year exhibitor retention at 76 per cent and retention of exhibit space sold at 78 per cent. Two points apart, which is a much narrower gap than the eleven points our single show produced.

That narrowness is a warning rather than a benchmark. Averaging self reported rates across a few hundred shows cancels the composition effects that make the measure worth computing in the first place, because one show losing anchors offsets another shedding small stands. The gap between your company rate and your space rate is a property of your own floor and it will not resemble an industry average.

Where this stops

Space sold and space occupied are different quantities, and the measure above uses the first.

An exhibitor who contracts 90 square metres and turns up with an unbuilt corner is retained at 90 in this arithmetic. An exhibitor who cancels three weeks out and forfeits a deposit may still sit in the contract table. If your space retention rate is computed from the contract file rather than from the final allocated floorplan, it will run a point or two above what the hall looked like, and the discrepancy is worth measuring once so you know its size.

The measure also says nothing about where the space is. 2,190 square metres released as a single block behind the seminar theatre is a different commercial problem from 2,190 square metres released as 90 scattered nine metre stands, and the second is harder to sell even though the arithmetic is identical. Any reporting on space retention that does not sit next to a floorplan is missing the part the sales team will care about first.

Two boundaries are worth naming explicitly. All of the above is net space, the sellable stand area, and the ratio between that and the gross hall area is its own decision with its own consequences. And a retention rate is a description of what happened, so turning it into next edition's booked space forecast needs per account probabilities and expected size changes, which is a different piece of work.

Pull the contracted square metres per exhibiting company for your last two editions, join them on account, and produce three totals: space held at edition N by companies that did not return, space released by companies that did return, and space added by companies that did return. Divide each by total space at edition N. Those three percentages plus 100 give you the space retention rate, and the middle one is almost certainly a number your renewal reporting has never shown anybody.