Media Briefings

Getting People To Give Blood: New Evidence On The Value Of Encouraging "Active Decisions'

  • Published Date: November 2011

People who have not previously thought much about the value to society of donating blood are much more likely to make a donation when they have been asked to make an ‘active decision’, yes or no. That is the central finding of experimental research by Alois Stutzer, Lorenz Goette and Michael Zehnder, published in the November 2011 issue of the Economic Journal.

Their study analyses a Red Cross blood drive in Switzerland, in which some people were asked to decide on the spot whether they were willing to donate. If these participants had thought about giving blood before, their likelihood of giving was unchanged; but if they hadn’t thought about it before, they were much more likely to give blood. The authors comment:

‘Our results suggest that gently nudging people to make a choice can have a powerful effect on altruistic or pro-social behaviour. Encouraging an active decision about whether or not to give blood can overcome initial reluctance, which might arise from not wanting to think about an unpleasant issue.

‘These findings can be applied to other areas where society as a whole might want to encourage more activity, such as organ donation or volunteering.’

What is the best way to encourage people to volunteer, to donate blood or to give money to charitable causes? While many individuals potentially benefit from such ‘pro-social’ activities, the costs are borne by the volunteers or donors alone. Thus, selfish people will often not contribute anything.

One of the big challenges facing the social sciences is to overcome this problem of ‘free-riding’. This study addresses the issue from a new angle. In some cases, individuals who do not contribute to a specific public good may not be against it in principle but have simply never thought about it. They have avoided pro-social activity because contemplating it may be unpleasant.

But some individual deliberation is often necessary to be convinced of the social value of a specific pro-social activity. For example, in the case of giving blood, the social benefits are clear as lives can be saved. But imagining oneself or others in such situations may be uncomfortable. Putting off thinking about such decisions avoids these thoughts, but also reduces the rate of blood donations.

This opens up a new opportunity to increase pro-social behaviour. These researchers propose and test the hypothesis that engaging undecided individuals in an ‘active decision’ to contribute or not to a specific public good, induces them to reflect on the issue.

This active decision mechanism (AD) thus helps them form a subjective value for the pro-social activity. Thus, making people think about donating blood, for example, can raise donations among individuals who have never actively considered it, while leaving the contributions of others unchanged.

The evidence for AD presented in the study is from a field experiment conducted as part of a Red Cross blood drive in the canton of Zurich, Switzerland. The researchers randomised participants into one of three different ‘treatments’ that they predicted would stimulate reflection about blood donations to different degrees:

  • In the baseline treatment, individuals were simply informed about the opportunity to donate in the blood drive.
  • In the strong AD treatment, people were not only informed about the blood drive but also asked to decide on the spot whether they were willing to donate and to indicate their decision on a sheet.
  • In the third treatment (the weak AD treatment), individuals had to choose whether they were willing to give blood but could also indicate that they did not want to decide at that moment.

The researchers also identified who had previously contemplated donating blood with the help of a survey question.

The study finds a strong differential effect of the AD treatment on two groups of potential donors: those who already felt sufficiently informed about giving blood did not respond to the AD treatment that asked them to make up their mind on the spot.

By contrast, those who had not previously reflected on the importance of donating blood had a much higher probability of donating in the strong AD treatment than in the baseline treatment. (The weak AD treatment was somewhere in between.) They were more likely to give blood by 8 percentage points, which is statistically significant. Given that the average sample donation rate was also about 8%, this is a very large effect.

Overall, these results suggest that active decisions are an effective means to increase pro-social behaviour in situations where contemplating a potential contribution may be unpleasant. Gently nudging individuals towards making a choice helps overcome initial reluctance and has a strong effect on pro-social behaviour. The results can be applied to other areas, such as organ donation policies.


Notes for editors: ‘Active Decisions and Prosocial Behaviour: A Field Experiment on Blood Donation’ by Alois Stutzer, Lorenz Goette and Michael Zehnder is published in the November 2011 issue of the Economic Journal.

Alois Stutzer and Michael Zehnder are at the University of Basel. Lorenz Goette is at the University of Lausanne.

For further information: contact Lorenz Goette on +41-21-692-3496 (email:; Alois Stutzer on +41-61-267-3361 (email:; or Romesh Vaitilingam on +44-7768-661095 (email: