Crowdsourced research spans citizen science, public-health projects, medical studies, and volunteer publishing. The figures below show how many people take part, where projects operate, what participants contribute, and how the research literature has developed.
Contents
- Participation at campaign scale
- NASA citizen science and discovery
- What volunteers actually contribute
- Who participates
- Crowdsourcing in health research
- Geography and global coverage
- The research literature on volunteering
Participation at campaign scale
SciStarter Citizen Science Month 2026 provides a large, time-bounded view of public participation. The campaign reached 450,918 volunteers from 140 countries. By April 30, 2026, participants had contributed 4,730,752 Acts of Science across more than 950 research projects and events. SciStarter Citizen Science Month 2026 reported the campaign as a month-long April effort, so these totals describe activity through that measurement date rather than a permanent annual total.
The campaign also set a goal of 2.50 million Acts of Science for April 2026. More than 400,000 volunteers contributed to that goal, and the final total was reported as 4.7 million Acts. The more precise April 30 figure was 4,730,752 Acts, while the rounded campaign summary used 4.7 million. Both figures refer to the same 2026 campaign and should not be treated as separate contributions.
Event participation was distributed through a substantial local network. SciStarter reported more than 480 events during Citizen Science Month 2026; another campaign count specified 481 events held worldwide in April. Around one-third of the 480-plus events were led locally by libraries and SciStarter Ambassadors, while about one-third of the 481 events were part of the Connected series. Libraries accounted for 34% of all Citizen Science Month events.
| Campaign measure | Reported figure | Measurement context |
|---|---|---|
| Volunteers | 450,918 | Citizen Science Month 2026 |
| Countries represented | 140 | Citizen Science Month 2026 |
| Projects and events | More than 950 | Citizen Science Month 2026 |
| Acts of Science by April 30 | 4,730,752 | April 2026 campaign |
| Worldwide April events | 481 | April 2026 |
| Library share of events | 34% | Citizen Science Month 2026 |
The campaign’s communication reach was larger than its direct volunteer count. Coordinated social-media efforts with partners reached 13 million people worldwide in April 2026. That is an audience-reach measure, not a count of people who completed a research task, so it should be read separately from the 450,918 volunteers.
NASA citizen science and discovery
NASA describes 36 citizen science projects as open to everyone, with no citizenship requirement. NASA’s news release on 23 new grants says NASA-funded citizen science projects have engaged roughly 1.5 million volunteers. The same source reports thousands of scientific discoveries and numerous scientific publications from those projects. These are broad program-level descriptions, not a single experiment’s participant count or publication total.
Volunteer authorship is one measurable form of research contribution. A NASA Science article dated May 5, 2026, reported that more than 650 NASA volunteers had co-authored peer-reviewed research papers with project scientists. NASA’s publications list, updated in February 2026, gives a more specific figure of 658 volunteers who had co-authored papers through NASA since 2011. The dates and wording differ, so the figures are best retained as source-specific counts rather than combined.
NASA’s publications list includes 20 named citizen-science project categories in its contents section. This category count describes the organization of the list, while the 658 figure describes volunteers credited as co-authors since 2011. Neither count is a measure of all people who submitted observations or classifications.
Planet Patrol shows how a crowdsourced workflow can be tied to a defined review batch. In its first batch, volunteers vetted 999 planet candidates and spotted 146 imposters. A second batch covered 1,998 candidates; 286 were identified as clear false positives and 251 more were flagged as potential planet impostors. Eleven Planet Patrol volunteers were co-authors on the paper about the 999 TESS planet candidates, according to NASA Science’s April 18, 2023 article.
What volunteers actually contribute
Crowdsourced research does not rely on one kind of task. Citizen Science Month recorded Acts of Science across more than 950 projects and events, while the Planet Patrol figures center on vetting candidate planets. The campaign also documented archival transcription: more than 200 pages were transcribed on April 10 for the Freedmen’s Bureau archive effort, producing 4,872 Acts of Science.
Cloudspotting on Mars illustrates the effect of concentrated participation. During one Connected event, participants generated more than 11,000 classifications in a single day. SciStarter reported that this was over 10 times the project’s typical daily average. During the event, Cloudspotting on Mars also crossed 20,000 registered participants. The classification burst is a one-day activity measure, whereas the registered-participant figure is a cumulative project threshold.
These examples show why crowdsourced research statistics need a clear unit of measurement. A volunteer count measures people, a classification count measures task outputs, a transcription-page count measures archival progress, and a registered-participant threshold measures project enrollment. They can describe the same initiative without being interchangeable.
The large Citizen Science Month totals provide scale, but the task-level examples provide texture. More than 11,000 Mars classifications, 4,872 archival Acts, and the review of 999 initial planet candidates each represent a different route from public participation to research-ready material. The sources do not provide a common conversion rate between these task types, so no combined productivity figure can be inferred.
Who participates
An online citizen-science study analyzed more than 14 million participant accounts from projects active from 1999 through 2021. PMC10662724 reported that rapid growth in participation during the early 2000s later diverged by participation mode. Nature-sensing projects continued to show consistent growth, while crowdsourcing and distributed-computing projects declined in the study’s reported pattern.
The same study found that most citizen-science projects outside nature sensing were heavily dominated by men, and that the vast majority of participants had a background in science. Those findings describe the study’s observed participant and project patterns across the analyzed online projects; they are not a demographic estimate for every crowdsourced research activity.
A separate citizen-science project characteristics study surveyed 838 participants. In that survey, 53% were at least 60 years old: 36.3% were aged 60 to 69 and 16.9% were aged 70 or older. The reported sex distribution was 52.6% female and 47.3% male.
Education and work status were also reported for the 838-person survey. Participants included 29.6% with a master’s or other postgraduate degree, 27.9% with a bachelor’s degree, and 19.8% who had completed technical or vocational training. Forty-eight percent were working and 45% were retired. Because these percentages come from a defined survey, they should not be presented as a universal profile of citizen scientists.
Crowdsourcing in health research
The health-and-medical crowdsourcing systematic review in PMC6971908 screened 3,508 citations, accessed 362 articles, and included 188 studies. Within the included evidence, 96 studies examined effectiveness, 127 examined feasibility, and 37 examined cost. These categories describe the review’s analytical scope; a study could contribute to more than one question, so the category counts should not be added as a total number of unique studies.
Evaluating surgical skills was the most common purpose identified in that review, covered by 17 studies. This gives a concrete indication of where health-and-medical crowdsourcing research was concentrated in the reviewed literature. It does not establish that surgical-skills projects are the largest form of crowdsourced research overall.
A separate public-health crowdsourcing scoping review identified 4,071 citations and included 74 studies. Of those studies, 35 were conducted in high-income countries, 15 in middle-income countries, and one in a low-income country. Eleven were conducted in multiple countries of varying income levels. The review therefore provides both a study count and an explicit geography classification for the included public-health evidence.
Geography and global coverage
The geography of crowdsourced research appears at several levels. Citizen Science Month 2026 reached volunteers in 140 countries, and its events were held worldwide. NASA’s citizen science projects were described as open to everyone without a citizenship requirement. The public-health scoping review, by contrast, classified included studies by country-income setting and found participation across high-, middle-, and low-income contexts, including multi-country studies.
These measures answer different questions. A country count indicates the geographic spread of a campaign’s volunteers. An open-access policy describes eligibility. A country-income classification describes where reviewed studies were conducted. None of these measures alone shows how evenly research opportunities or outputs were distributed among countries.
The library figure adds another dimension of reach: 34% of Citizen Science Month events took place in libraries. The campaign also reported that around one-third of more than 480 events were led locally by libraries and SciStarter Ambassadors. These figures point to community venues as an important participation channel, while the sources do not provide comparable venue data for NASA projects or the health reviews.
The research literature on volunteering
A biomedical volunteering bibliometric analysis found 3,555 research articles on volunteering. Those articles appeared across 1,283 journals and covered journals spanning 110 specialties. Only 51 journals published 10 or more volunteering articles, while the bibliography identified 10,853 authors across the articles.
The distribution of authorship was highly diffuse in the reported bibliography. Only eight authors published more than 10 volunteering research articles. The publication count grew from one article in 1953 to 254 articles in 2016. The 1953 and 2016 values are historical publication counts in that analysis, not current annual totals or a forecast.
Taken together, the available figures describe crowdsourced research as both a participation system and a research subject. Citizen Science Month measured hundreds of thousands of volunteers and millions of task outputs in one April campaign. NASA documented open projects, volunteer co-authorship, and defined candidate-review batches. Health reviews measured the size and focus of an evidence base, while bibliometric work tracked the growth and dispersion of volunteering research across journals and specialties. The measurement period, unit, and source label remain essential whenever these statistics are compared.