Week in charts
Delta’s dominance

Heatwaves • Facebook’s clout • American house prices • Entertainment habits

IN THE LAST months of 2020 researchers around the world began to see variants of SARS-CoV-2 with not just one or two mutations but ten or 20. Some of these new variants turned out to have new properties—they could spread faster, shrug off antibodies, or both. First Alpha appeared in Britain in September 2020; then came Beta in South Africa and Gamma in Brazil. Each infection with the original virus, as sequenced in Wuhan in January 2020, had been estimated to lead to roughly 2.5 subsequent infections in the absence of countermeasures. Under the same conditions the “reproductive number” for Alpha was reckoned to be almost twice as large: four or five. British scientists estimate that in unvaccinated populations the reproductive number of the Delta variant, a key factor in the catastrophic Indian epidemic in recent months, may be as high as eight. It now threatens the world.

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Heatwaves may generate headlines—as with the broiling of America’s Pacific Northwest and western Canada—but less attention is paid to them than they deserve. Heat is a silent killer, its victims often apparent only in retrospect, as statisticians tot up excess deaths and hospital admissions. Climate change will make heatwaves more common and more extreme. Even if greenhouse-gas emissions are cut to net-zero by the middle of this century, temperatures will go on rising for decades.

An antitrust case against Facebook fell apart in the past week partly because the Federal Trade Commission (FTC), which lodged it, failed to explain precisely what market the company dominates. To do so is hard. Like Facebook, most social-media firms do not charge users, so the typical approach of looking at an industry’s consumer-derived sales is no use. Facebook does have paying customers, firms that buy ads on its platforms, but the extent of that market, too, is hazy. According to an estimate by The Economist, if all American online advertising counts, Facebook’s share is 25%. But its share of social-media advertising alone is 60%.

House prices in America rose by 14.6% in the year to April. That is the fastest rate in the 34-year history of a widely watched index compiled by S&P Global, a financial-information firm. Houses listed for sale are on average snapped up in just 17 days, a record low. Low mortgage rates, a function of prevailing yields on mortgage-backed securities, tend to entice would-be homebuyers. Given that the housing market is already fired up, it might seem odd that the Federal Reserve is juicing it further by buying mortgage-backed securities and suppressing mortgage rates. At the Fed’s monetary-policy meeting last month Jerome Powell, its chairman, made clear that the central bank is not yet ready to stop buying assets, but has begun to discuss when to do so.

As entertainment options outside the home were shut down in a bid to stop the spread of coronavirus, and commuting gave way to home-working, people had time on their hands. Consumption of everything from books and podcasts to music and video games shot up. As the amount of spare time at home starts to shrink, the attention boom of 2020 is giving way to what Mark Mulligan of MIDiA Research, a firm of analysts, dubs an “attention recession”. The question is which newly acquired habits will stick and which will be dropped. As well as hastening the switch from old to new formats, covid-19 has shown how different sorts of media increasingly compete with each other for consumers’ attention.

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