Some years ago, the Nobel Prize-winning economist Richard Thaler thought of doing an experiment in which people would be given lottery tickets to encourage them to take the flu vaccine. Too bad he and his academic partner ended up not doing it. The results would have been quite relevant today. The world, or at least the rich parts of it, have gone from having no vaccine for Covid-19 to too many doses with people in places such as Hong Kong refusing or hesitant to take the free shots. Cities across the United States have responded by offering a vaccine lotto and prizes, including scholarships. Back in Hong Kong, Sino Group, the Ng Teng Fong Charitable Foundation and Chinese Estates Holdings are jointly offering a one-bedroom flat measuring 449 sq ft worth HK$10.8 million in Kwun Tong as the grand prize. Other private companies are giving out discounted hotel room rates, shopping coupons, air tickets and a HK$500,000 electric car . The Hong Kong government and some firms, including investment banks, are offering paid vaccine leave days. The winner of another prize can host a private party on a plane. The US$14.5 million in lottery prizes, perks for vaccinated Hongkongers The inducements are effectively real-life experiments that offer a wealth of data to social scientists such as Thaler, who pioneers what is called behavioural economics. It wouldn’t be surprising if the first people in the US who proposed holding a Covid-19 lotto are specialists in such disciplines. In popular science, the studies are called “nudge theory”, according to which people are cognitively biased in predictable ways and can be gently pushed into doing things that are good for them, but which they may be reluctant to do, such as eating more vegetables and less meat. The British and Australian governments both have “nudge” units to study and propose innovative public policies, as does the provincial government of British Columbia in Canada. An Organisation for Economic Cooperation and Development study published in November counted more than 200 institutions in its member states that now apply behavioural insights to public policy. In Hong Kong, between May 27 – the day before the announcement of the flat prize – and June 3, the daily number of people who received their jabs leapt by 38.5 per cent, from 26,144 to 36,209, with the rise mainly from those receiving the Chinese-made Sinovac vaccine, a 61 per cent increase. A triumph of social science or just common sense?