Incidence rate: definition, formula, and examples

Incidence rate (IR) is the percentage of people in a survey who qualify to complete it after screening. The formula is simple:

IR = qualified respondents / total respondents x 100

If 500 people start a survey and 150 pass the screening questions, the incidence rate is 30%. That single number predicts how much a study will cost and how long it will take to field, which is why it's one of the first things a market research team calculates before writing a single question.

Incidence rate matters because it sets the ceiling on how efficiently you can reach your target audience.

A survey with a 60% IR needs roughly two people invited for every one completed response. A survey with a 5% IR needs 20. Every one of those extra invitations costs money, whether you're paying per completed response through a panel or spending internal time chasing down respondents.

Low incidence rate survey research isn't just slower, it changes the entire budget conversation.

A general consumer survey targeting "adults who drink coffee" screens in almost everyone.

A survey targeting "IT directors at hospitals with over 500 beds who evaluated a new EHR platform in the last six months" screens in almost nobody, and every qualified respondent costs proportionally more to find.

This is also where feasibility and incidence rate intersect.

Before a research team commits to a timeline, they need to know whether the target population is large enough, and rare enough, that the study is even practical to field within budget.

A qualification rate under 10% on a general population panel is often a signal to narrow the sample source, adjust the target definition, or extend the field window before committing to a launch date.

The formula stays the same regardless of your audience: divide qualified respondents by total respondents, then multiply by 100. What changes is how narrow your target population is, and that's what actually drives the number up or down.

A brand wants feedback from anyone who has ordered takeout in the last month. Out of 800 people who start the survey, 640 qualify. IR = 640 / 800 x 100 = 80%. Broad, everyday behaviors screen in almost everyone, so this survey fields quickly and cheaply.

A B2B software company wants feedback from operations managers at manufacturing companies with 100 to 500 employees who use a shift-scheduling tool. Out of 600 people invited, 96 qualify. IR = 96 / 600 x 100 = 16%. This is a realistic mid-range incidence rate: specific enough to require real screening, common enough that the audience isn't impossible to find.

A medical device maker needs feedback from cardiologists who have performed a specific minimally invasive procedure in the last year. Out of 400 healthcare professionals invited, 18 qualify. IR = 18 / 400 x 100 = 4.5%. This is a low incidence rate survey by any standard, and it typically requires a specialty panel, a longer field period, and a higher cost per completed response.

Notice what stays constant across all three: the formula. What changes is the denominator problem, how rare your qualifying respondent actually is in the population you're sampling from.

Incidence rate rarely travels alone. These related terms come up in the same conversations, and mixing them up is a common source of confused project scoping.

Incidence rate varies enough by category that it's worth sanity-checking your assumptions against how other teams typically plan. These are general, illustrative patterns rather than fixed benchmarks, and actual rates shift based on how tightly a study defines its target audience.

Customer experience research aimed at existing customers of a specific product tends to run on the higher end, since the sample is often pulled directly from a customer list rather than a general panel, and the target group is already known to include qualifying respondents.

HR and employee experience surveys inside a single organization typically see very high incidence rates, close to 100%, because the entire invited population is already the target population. Incidence rate becomes a bigger factor in HR-adjacent research only when a study reaches outside the organization, such as benchmarking against external labor market segments.

Healthcare and specialty B2B research tends to run lowest, especially when targeting specific clinical roles, rare conditions, or narrow purchasing committees. A study targeting a specific medical specialty combined with a specific facility type can see incidence rate estimates well under 10%, which is why these studies often need longer field windows and specialty panel sources built for the vertical.

Screening questions are the mechanism behind every incidence rate calculation, and the SurveyMonkey guide to using screening questions covers how to write and sequence them inside a survey. For help defining the target population itself before you start estimating IR, see identifying your target market. Once you know roughly how rare your audience is, the sample size calculator helps translate that into how many people you actually need to invite.

Incidence rate is the number that turns a research idea into a real budget and timeline. Estimate it early, with a pilot or a soft launch, and you'll avoid the most common planning mistake in market research: committing to a completion date before anyone checks whether the target audience is actually reachable at the volume the project needs.

Estimate your incidence rate with SurveyMonkey Audience or browse market research survey templates to get your next study moving.