For a second year, Covid-19 has scuttled the traditional formal banquet in Stockholm attended by winners of the prizes in chemistry, physics, medicine, literature and economics, which were announced in October.
Natural experiments provide an opportunity to study the effect of programmes and policies such as rural electrification and iron supplementation, as well as of uncontrolled events such as famines.
David Card, Josh Angrist and Guido Imbens pushed economics closer to the traditional sciences with experiments that mimicked the randomised trials in drug tests.
Philippines President Rodrigo Duterte's office on Monday congratulated journalist Maria Ressa for winning the Nobel Peace Prize, calling it "a victory for a Filipina" for which it was happy to see.