How effective is Germany’s COVID-19 contact tracing app?

New study published in Nature Human Behavior led by Hertie School researchers suggests that monetary incentives could lead to increased uptake.

New research by Hertie School Assistant Professor of Data Science and Public Policy Simon Munzert shows that Germany's contact tracing “Corona Warn-App” is underused by those who have heightened risk of exposure to COVID-19. Munzert and his co-authors, Anita Gohdes, Professor of International and Cyber Security, and Senior Research Scientist William Lowe (both from the Hertie School), as well as Peter Selb from the University of Konstanz and Lukas Stoetzer from the Humboldt University of Berlin, show that monetary incentives – even small ones – can dramatically increases the number of downloads, especially among young people.

“Our results suggest that monetary incentives can mobilize additional compliance when information and arguments have reached their limits in motivating app usage,” says Munzert.

Since the coronavirus outbreak, digital contact tracing apps have been introduced globally as a tool by governments to help contain the pandemic. In Germany, the Corona Warn-App was developed by SAP and Deutsche Telekom.

The app uses a so-called “privacy by design” approach, which ensures it only collects a minimum amount of personal data, that is handled with maximum protection. The focus on privacy has led to a wider acceptance of the tracing app in Germany, but also makes it more difficult to evaluate effectiveness.

After high adoption rates in the first weeks after its launch in June, uptake of the Corona Warn-App has been stagnating. The study was designed to both track download rates over a period of about 100 days and understand how to stimulate usage. The results suggest that, at the beginning of the study period higher proportions of vulnerable groups used the app, while individuals with more frequent social contact were less likely to use it.

“While surveys can be useful to learn about individuals’ behaviours, relying on self-reporting can lead to biases. We managed to overcome this challenge by combining survey responses with fine-grained tracking data, allowing us to actually see whether our research participants were using the app,” Munzert says. “We randomly sent informative messages designed to motivate the survey participants to install the app, and subsequently compared their app usage through survey and tracking data to those who didn’t receive these messages.”

Based on a second experiment conducted by the researchers, the study reveals that informative and motivational video messages help to educate the public on the coronavirus, but have a very limited effect on the number of downloads. Monetary incentives, however, did lead to increased acceptance, especially among younger participants.

“In a second experiment, we randomly assigned individuals into two groups: one group was offered a financial incentive to download the app (either 1, 2, or 5 EUR), while the other group was not asked or incentivized to install the app,” Munzert explains.

The results of the study support scepticism about the current effectiveness of the app, but at the same time show optimism about its potential to increase it by expanding the user base through incentives.
“Despite the fact that app usage was already quite high, our results show a 17 percentage point increase in app usage for those who were offered a financial incentive,” Munzert says.

Therefore, incentivizing people to download the app, especially those that engage in risky behaviour and have more social interactions, would greatly improve the app’s reliability and ability to protect populations.

Read the full study here.

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