How many citizen scientists in the world?

Since the development of the proposal for the Doing It Together Science project (DITOs), I have been using the “DITOs escalator” model to express the different levels of engagement in science, while also demonstrating that the higher level have fewer participants, which mean that there is a potential for people to move between levels of engagement – sometime towards deeper engagement, and sometime towards lighter one according to life stages, family commitments, etc. This is what the escalator, after several revisions, look like:

I have an ongoing interest in participation inequality (the observation that very few participants are doing most of the work) and the way it plays out and influences citizen science projects. When you start attaching numbers to the different levels of public engagement in science, participation inequality is appearing in this area, too. Since writing the proposal in 2015, I have been looking for indications that will support the estimation of the number of participants. During the process of working on a paper that uses the escalator, I’ve done the research to identify sources of information to support these estimations. While the paper is starting its peer review journey, I am putting out the part that relates to these numbers so this part can get open peer review here. I have decided to use 2017 as a recent year for which we can carry out the analysis. As for geographical scale, I’m using the United Kingdom as a country with very active citizen science community as my starting point.

At the bottom of the escalator, Level 1 considers the whole population, about 65 million people. Because of the impact of science across society, the vast majority, if not all, will have some exposure to science – even if this is only in the form of medical encounters.

However, the bare minimum of engagement is to passively consume information about science through newspapers, websites, and TV and Radio programme (Level 2). We can gauge the number of people at this level from the BBC programmes Blue Planet II and Planet Earth II, both focusing on natural history, with viewing figures of 14 million and about 10 million, respectively. We can, therefore, estimate these “passive consumers” at about 25% of the population.

At the next level is active consumption of science – such as visits to London’s Science Museum (UK visitors in 2017 – about 1.3), or the Natural History Museum (UK visitors in 2017 – about 2.1m), so an estimation of participation at 10% of the population seem justified.

Next, we can look at active engagement in citizen science but to a limited degree. Here, the Royal Society for the Protection of Birds (RSPB) annual Big Garden Birdwatch requires the participants to dedicate a single hour in the year. The project attracted about 500,000 participants in 2017, and we can, therefore, estimate participation at this level at about 1% of the population. This should also include about 170,000 people who carried out a single task on Zooniverse and other online projects.

At the fifth level, there are projects that require remote engagement, such as volunteer thinking on the Zooniverse platform, or in volunteer computing on the IBM World Community Grid (WCG), in which participants download a software on their computer to allow processing to assist scientific research. The number of participants in WCG from the UK in 2017 was about 18,000. In Zooniverse about 74,0000 people carried out more than a single task in 2017, thus estimating participation at this level at 0.1% of the population (thanks to Grant Miller, Zooniverse and Caitlin Larkin, IBM for these details).

The sixth level requires the regular data collection, such as the participation in the British Trust of Ornithology Garden Birdwatch got about 6,500 active participants in 2017 (BTO 2018), while about 5000 contributed to the biodiversity recording system iRecord (thanks to Tom August, CEH) and it will be reasonable to estimate that the participation is about 0.01% of the population.

The most engaged level include those who are engaged in DIY Science, such as exploring DIY Bio, or developing their own sensors, etc. We can estimate that it represents 0.001% of the UK population at most (thanks to Philippe Boeing & Ilia Levantis).

We can see that as the level of engagement increases, the demand from participants increase and the number of participants drops. Not that this is earth-shattering, though what is interesting is that the difference between levels is in order of magnitude. We also know that the UK enjoys all the possible benefits that are needed to foster citizen science: a long history of citizen science activities, established NGOs and academic institutions that support citizen science, good technological infrastructure (broadband, mobile phone use), well-educated population (39.1% with tertiary education), etc. So we’re talking about a best-case scenario.

It is also important, already at this point, to note that UNESCO’s estimates of the percentage of UK population who are active scientists (working in research jobs), is 0.4% which is bigger than the 0.111 for levels 5,6 and 7.  

Let’s try to extrapolate from the UK to the world.

First, how many people we can estimate to have the potential of being citizen scientists? We want them to be connected and educated, with a middle-class lifestyle that gives them leisure time for hobbies and volunteering.

The connectivity gives us a large number – according to ITU, 3.5 Billion people are using the Internet. The estimation of the size of middle-class is a bit smaller, at 3.2 Billion people.  However, we know that participants in most citizen science projects which use passive inclusiveness, where everyone is welcome without an active effort in outreach to under-represented groups, tend to be from people with higher education (a.k.a tertiary education). There is actually data about it – here is the information from Wikipedia about tertiary educational attainment. According to UNESCO’s statistics, there were over 672 million people with a form of tertiary education in 2017. Let’s say that not everyone in citizen science is with tertiary education (which is true) so our potential starting number is 1 Billion.

I’ll assume the same proportion of the UK, ignoring that it present for us the best case. So about 250 million of these are passive consumers of science (L2), and 100 million are active consumer (e.g. going to science museums) (L3). We can then have 10 million people that participate in the once a year events (L4); 1 million that are active in online citizen science (this is more than a one-off visit or trial) (L5); about 100,000 who are the committed participants (mostly nature observers) and about 10,000 DIY bio, makers, and DIY science people (L6 and L7).

Are these numbers make sense? Looking at the visits to science/natural history museums on Wikipedia, level 3 seems about right. Level 4 looks very optimistic – in addition to Big Garden Birdwatch, there were about 17,000 people participating in City Nature Challenge, and 73,000 participants in the Christmas Bird Count, and about 888,000 done a single task on Zooniverse – it looks like that a more realistic number is 3 million or 4 million. Level 5 is an underestimate – IBM Word Community Grid have 753,000 members, and there are other volunteer computing projects which will make it about 1 million, then there were about 163,000 global Zooniverse contributors (thanks to the information from Grant Miller), 130,000 Wikipedians, 50,000 active contributors in OpenStreetMap, and other online projects such as EyeWire etc. So let’s say that it’s about 1.5 Million. At level 6, again the number is about right – e.g. eBird reports 20,000 birders in their peak day. For the sake of the argument, let’s say that it’s double the number – 200,000. Level 7 also seems right, based on estimations of biohackers numbers in Europe.

Now let’s look at the number of scientists globally: in 2013 there were 7.3 million researchers worldwide. With the estimation of “serious” citizen scientists (levels 5,6 and 7) at about 1.7 million, we can see the issue of crowdsourcing here: the potential crowdsourcer community is, at the moment, much bigger than the volunteers.

Something that is important to highlight here is the amazing productivity of citizen scientists in terms of their ability to analyse, collect information, or inventing tools – we know from participation inequality that this tiny group of participants are doing a huge amount of work – the 50,000 OSM volunteers are mapping the world or the 73,000 Christmas Bird Count participants provided 56,000,000 observations or the attention impact of the Open Insulin Project. So numbers are not the only thing that we need to think about.

Moreover, this is not a reason to give up on increasing the number of citizen scientists. Look at the numbers of Google Local Guides – out of 1 Billion users, a passive crowdsourcing approach reached 50 million single time contributors, and 465,000 in the equivalent of levels 5 to 7. Therefore, citizen science has the potential of reaching much larger numbers. At the minimum, there is the large cohort of people with tertiary education, with at least 98 million people with Masters and PhD in the world.

Therefore, to enable a wider and deeper public engagement with science, apart from the obvious point of providing funding, institutional support, and frameworks to scale up citizen science, we can think of an “escalator” like process, which makes people aware of the various levels and assists them in moving up or down the engagement level. For example, due to a change in care responsibilities or life stages, people can become less active for a period of time and then chose to become more active later. With appropriate funding, support, and attention, growing the global citizen science should be possible. 

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