A guide to the most concerning, striking and downright extraordinary numbers of 2021. Tim Harford asks three More or Less interviewees about their most significant and memorable figure over the past year. From the excess death toll of Covid-19; to declining total fertility rates, and a spike in the concentration of carbon dioxide in the atmosphere, we showcase the numbers that tell us something about the year gone by.

During this programme, we speak to Hannah Ritchie, head of research at Our World in Data and senior researcher at the University of Oxford; Marina Adshade, Economics Professor at the University of British Columbia; and Heleen De Coninck, professor at Eindhoven University of Technology, and a lead author on several reports by the Intergovernmental Panel on Climate Change.