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OVER the past month, successive waves of thick smog have blanketed northern and central China. With visibility severely reduced, authorities have cancelled flights, shut highways and imposed emergency factory closures. Air quality usually deteriorates during the winter when demand for heating soars and coal-fired power plants rev up. But after the government declared a “war on pollution” in 2014, China had in fact made some headway in improving its environment. With stricter emission standards on power plants, it worked to curb its reliance on coal. Smog, though still too frequent, was at least a bit lighter.

What explains the reversion to “airpocalypse”?

WHEN it was finally released on December 15th, “Super Mario Run” quickly became the most downloaded free game in Apple’s app stores in 138 countries. At last count well over 50m people had downloaded it. In contrast, all Super Mario titles released over the past three decades have together sold some 558m copies. The numbers were not surprising: “Super Mario Run” is the pudgy plumber’s first outing for smartphones, which over the past decade have become the prefered choice of device for casual gamers.

CHRISTMAS shopping is hard. You never really know what others want. If Homo economicus had his way, Christmas presents, to the extent that they would exist, would only come in the form of cash—thus allowing recipients to buy exactly what they desire. To Homo sapiens however, giving cash feels transactional (and distinctly un-Christmassy).

A marginally less offensive present is the gift card. Britons now spend around £6bn a year ($7.4bn) on gift vouchers, up from about £2bn in 2010. The fact that gift cards are almost as good as cash has surely contributed to their popularity.

MAPS commonly used in schools rely heavily on a contorted version of the world from an earlier age in history. The map most widely adopted for educating youngsters was created by Gerardus Mercator, a Flemish geographer and cartographer, in 1569. The projection keeps parallels (circles of latitude) and meridians (lines of longitude) straight and perpendicular to each other, which was vital for 16th century navigators. But its main failing is that it distorts country shapes and areas towards both poles, in common with all cylindrical projections. Near the equator the inaccuracies are small and the true shape of countries is well represented.

IT’S THE most wonderful time of the year, sang Andy Williams, the 1960s crooner. Retailers cannot disagree. This year, holiday shoppers will boost retail sales by 15-35% in much of the rich world compared to seasonally-adjusted sales. In America alone, the increase in spending will total more than $75bn.

But recent trends suggest that holiday shoppers may be growing less jolly. In 2000, Americans spent 29% more in December than they would have without the seasonal effect of the holidays. By 2015, this figure had fallen to 21%. Several other rich countries including Germany, Japan and France have experienced a similar decline in seasonal retail activity.

RESETTLEMENT is one of the thorniest problems caused by the surge of migrants in Europe. Politicians and pundits frequently debate how to integrate newcomers, and how well they will cope thereafter. If the progress of the continent’s Roma population is anything to go by, the new arrivals could be bound for a destitute existence. A new survey by the European Union Agency for Fundamental Rights (FRA) paints a grim picture of living conditions for the continent’s largest ethnic minority.

Overall, 17% of residents of EU countries are at risk of poverty. According to the FRA, among Roma that share is 80%.