What it is
Before you add AI, record the figure you want to improve: minutes per case, cases per hour, error rate. That figure is your baseline. After AI is in place, measure the same thing the same way and compare.
What the evidence shows
Published results differ widely, so someone else’s figure tells you little about your own.
- An experiment on writing tasks found a 40% cut in time.
- A study of customer-support agents at work found 15% more issues resolved per hour.
- A study of the Danish labour market found no change in earnings or hours. An earlier version put average time savings at 2.8%.
The three do not contradict each other. The first two studies measured one well-chosen task. The third measured everyone who had access to a chatbot.
People’s own estimates are a poor guide, so measure rather than ask.
- Staff can feel faster and be slower. In a randomised trial with 16 experienced software developers, each of 246 real tasks was randomly allowed or barred from using AI. Tasks took 19% longer with AI. Beforehand, the developers expected AI to make them 24% faster. Afterwards, they believed it had made them about 20% faster.
- National self-reports are small. In an online survey series of US adults run by the economists Bick, Blandin and Deming, employed people put the time generative AI saves them at 2.17% of all their work hours in the second quarter of 2026. That figure is self-reported.
Reported returns are a different thing again. In a survey by IDC for Microsoft, which sells AI tools, business leaders reported an average return of $3.50 for each $1 invested in AI. That figure is what leaders said, not a measurement. When nearly 6,000 executives in four countries were asked, nine in ten reported no effect of AI on their firm’s productivity or employment over the past three years.
How to do it
- Pick one or two measures per task: time per case, and one quality measure.
- Record them for a few weeks before the change. Use system logs where you can, not estimates. You cannot rebuild a baseline afterwards. When the developer trial above was rerun in 2026, many developers would not work without AI, and 30–50% held back tasks they did not want to do without it, so the comparison failed. At four endoscopy centres in Poland, doctors’ detection rate in colonoscopies done without AI had already fallen from 28.4% to 22.4% three months after AI arrived. A “without AI” figure taken after rollout makes the AI look better than it is.
- Change one thing at a time.
- Measure again once people are past the learning period.
- If you can, keep a group working the old way for comparison. Set it up at the start. Once people are used to the tool, they refuse the old way or choose which tasks go into it.
- Count checking and correction time as part of the new process.
- Report the result even when it is small or negative.
What to measure
- Time per case or cases per hour.
- A quality measure: error rate, rework, customer complaints.
- Checking time added by AI.
- Sales or fees per job, and whether your prices changed. Time saved and money earned can diverge. Among US small employer firms using AI, 71% told a Federal Reserve survey their productivity had risen, and 31% that their sales had risen.
- Outside spending avoided. In the same survey, 18% of firms using AI had cut their spending on outside services.
- Work that was not being done before: unanswered enquiries, products with no description. In randomised experiments on a large online retail platform, the largest sales gain, 16.3%, came from a chatbot answering buyers who had previously had no live help at all.
- An objective quality measure, not only customer ratings. In a field experiment in Alibaba’s customer service, AI help raised customer ratings, but customers came back with the same problem just as often. The study is a working paper, not yet peer-reviewed.
- Output per day, when people run several AI tasks at once. In the 2026 rerun of the developer trial, time per task stopped being reliable once developers ran several AI agents in parallel.
To see how many minutes a week each person must save to cover the costs, put your figures into Will AI pay back?.
Where it fails
- Self-reported time savings. People’s estimates can get the direction wrong, not only the size. The developers above felt faster and were slower. Two UK government evaluations of the same office assistant also differ. Across government, users said Microsoft 365 Copilot saved them 26 minutes a day. HMRC, the UK tax authority, gave 3,000 licences to staff chosen at random and cut the self-reported figures by about 20% for bias. It found about 60 minutes a week. Both figures are what staff said. See the claim check on the 26 minutes. Use logs or timed samples.
- Speed without quality. A faster process that produces more errors is not a gain.
- Saved time that goes nowhere. Minutes saved per task matter only if the time is put to use. In a field experiment with 7,137 workers at 66 firms, workers given an office AI assistant spent about two hours less on email a week, and the amount and mix of their other work did not change. Three of the four authors worked for Microsoft, which sells the assistant. Decide in advance what the time will be used for.
- Billing by the hour. If you charge clients for time, an hour AI saves is an hour you can no longer bill, unless you change how you price. Clio, which sells legal software, reports that in its 2026 survey 86% of solo lawyers and 78% of small law firms had made no pricing change because of AI. Before you count the time saved as a gain, decide whether you will charge by the job, a fixed fee or the hour, and what that does to your fees.
- Work that is hard to count. For varied expert work, compare samples of output, not minutes.
By company size
- Micro and small: a spreadsheet and a two-week tally are enough. Note your sales or fees per job in the same sheet. If you bill by the hour, decide how you will price before you bank the time saved.
- Mid-market and enterprise: use workflow system data, and agree the measures with finance before the project starts, so the result is accepted afterwards.
See it applied
Company cases
Companies that did this
- Ashurst The firm timed set tasks under controlled conditions. It also had senior lawyers score AI drafts and lawyers’ drafts without knowing which was which.
- eBay Sales were compared before and after the change, and against countries where nothing had changed.
- Herges Stahl- und Blechbau The firm first built a way to record real production times. Its earlier hand-kept records differed by up to 30 minutes for identical parts.
- Hitachi Energy One production batch was split into four groups. One group was made the usual way, and the other three with one or both of the suggested changes.
- HM Revenue & Customs (HMRC) HMRC picked licence holders at random instead of only taking volunteers, and reduced self-reported time savings by about 20% because survey respondents were likelier to be active users.
- Klarna Klarna reported image production time before and after: 6 weeks down to 7 days, checks included.
- Klarna Klarna reported resolution time before and after (11 minutes down to under 2), along with repeat enquiries and satisfaction.
- PSG Global Solutions Applicants were assigned at random to an AI or a human interviewer, so the two groups could be compared directly.
- Rue La La For five months, sets of competing products were assigned either to the recommended prices or to the old prices, and the two were compared.
- SAM The firm reports each result against the figure before: hours per file, weeks to collect documents, share of incomplete files.
- Siemens Every worker judged the same 200 product images under the same time limits, and the answers were scored against the known correct result.
- Temple & Webster Customer care cost is reported as a share of revenue against the 2023 level. AI reviews of the product range were compared with reviews done by hand.
- UK Department for Business and Trade The evaluators did not rely on what users said. They timed the same tasks for users and non-users and had the results scored blind.
What happened without it
Sources
- Humlum and Vestergaard (2025). Still Waters, Rapid Currents: Early Labor Market Transformation under Generative AI. NBER Working Paper 33777 (revised March 2026). What this study did and found
- Brynjolfsson, Li and Raymond (2025). Generative AI at Work. The Quarterly Journal of Economics, 140(2), 889–942. What this study did and found
- Noy and Zhang (2023). Experimental evidence on the productivity effects of generative artificial intelligence. Science, 381(6654), 187–192. What this study did and found
- Becker, Rush, Barnes and Rein (METR) (2025). Measuring the Impact of Early-2025 AI on Experienced Open-Source Developer Productivity. METR, published 10 July 2025 (arXiv 2507.09089); follow-up published 24 February 2026. What this study did and found
- Dillon, Jaffe, Immorlica and Stanton (2025). Shifting Work Patterns with Generative AI. NBER Working Paper 33795; arXiv 2504.11436, version 4 (November 2025). What this study did and found
- Budzyń, Romańczyk, Kitala and colleagues (2025). Endoscopist deskilling risk after exposure to artificial intelligence in colonoscopy: a multicentre, observational study. The Lancet Gastroenterology & Hepatology, 10(10), 896–903. What this study did and found
- Federal Reserve Banks (2026). Small Business Credit Survey: 2026 Report on Employer Firms. Federal Reserve Banks, Small Business Credit Survey (published March 2026). What this study did and found
- Fang, Yuan, Zhang, Donati and Sarvary (2025). Generative AI and Sales Productivity: Field Experiments in Online Retail. arXiv 2510.12049, version 6 (29 June 2026). What this study did and found
- Yotzov, Barrero, Bloom, Bunn, Davis, Foster, Jalca, Meyer, Mizen, Navarrete, Smietanka, Thwaites and Wang (2026). Firm Data on AI. NBER Working Paper 34836 (February 2026, revised March 2026). What this study did and found
- Microsoft (2023), reporting IDC survey research: an average return of $3.50 per $1 invested in AI, as reported by business leaders. blogs.microsoft.com
- Bick, Blandin and Deming. Generative AI, time savings: employed adults (series RPSGENAITSALL), from the Real-Time Population Survey, an online survey of US adults. Federal Reserve Bank of St. Louis, FRED. fred.stlouisfed.org
- UK Government Digital Service (2 June 2025). Microsoft 365 Copilot experiment: cross-government findings report. gov.uk
- Ni, Wang, Feng, Lu, Wang and Zhou (2026). Generative AI in Action: Field Experimental Evidence from Alibaba's Customer Service Operations. arXiv 2603.29888. Working paper, not peer-reviewed. arxiv.org
- Clio (2026). Legal Trends for Solo and Small Law Firms. Press release. Clio sells legal software with AI built in. clio.com
Claims on this topic, checked against these studies:
- “66% of small businesses use AI” Needs correcting
Related practices
- Start with one costly process, not a company-wide rollout Pick one process that visibly costs time or money. Apply AI there, with a person checking the output, and expand only when the numbers move. Do first · Effort: medium (weeks, a few people)
- Do not treat a maturity score as a forecast An AI maturity or readiness score describes where you say you stand. Evidence that a higher score leads to better results is thin and disputed. Use it to start a discussion, not to predict returns. Do next · Effort: low (days, one person)
- For each kind of task, test whether a person with AI beats either one alone Do not assume that adding a person to AI, or AI to a person, gives the best result. Test it for each type of task before you settle the process. Do next · Effort: medium (weeks, a few people)