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The relationship between wealth, happiness and inequality

ECONOMISTS, trying hard to dispel a stubborn reputation as a gloomy bunch, have become fascinated with the relationships between wealth, inequality and happiness. There is evidence, at both an individual and a country level, of a relationship between income and happiness. Rich Denmark is happier than poorer China. But there are interesting wrinkles within that.

The energy efficiency of computing is doubling every 18 months

IN 1965 Gordon Moore, a co-founder of Intel, first observed that integrated circuits, better known as silicon chips, seemed to conform to a predictable law: since their invention in 1958, the density of components in each chip had doubled each year, and this trend was, he suggested, likely to continue for at least a decade. In 1975 Dr Moore modified his prediction, observing that component density was doubling every two years. In practical terms, the result is that personal-computer performance doubles every 18 months, and has done so for decades, a prediction commonly known as Moore's law.

A global picture of homicide rates

IT IS famously tricky to compare crime statistics across frontiers. Murder figures are the best of the bunch because the offence is usually reported. According to the first global study on homicide by the United Nations Office on Drugs and Crime, most of the world's 468,000 intentional homicides in 2010 were in Africa (36%) and the Americas (31%), where the murder rate was 15-16 per 100,000 people, more than twice the global average of 6.9 per 100,000. Homicide in most parts of the world has been falling since 1995, but it has risen recently in Central America and the Caribbean.

Bank share prices are close to their 2008-09 lows 

WILD gyrations in stockmarkets; banks' share prices falling like stones; politicians stepping in to back-stop lenders for fear of collapse. The echoes of 2008 are alarming. Morgan Stanley is one of the big casualties: fears apparently caused by its exposure to European assets led its share price to fall by 17% over the past two days of trading. You have to go back to December 3rd 2008 to find the last time the bank's stock closed at the same price as it did on October 3rd, even if it still sits 36% above its 2008 nadir.

The emerging markets are winning the currency war

A YEAR ago Brazil's finance minister, Guido Mantega, declared that the world had entered into a “currency war”. He worried that in a depressed global economy, without enough spending to go around, countries would sally forth and grab a bit of extra demand for themselves by weakening their currencies. The dollar, for example, fell by 11% against Brazil's real in the year to August 2011. Like other emerging economies, Brazil fought back by imposing taxes and other restrictions on foreign purchases of local securities. But the invasion of foreign capital that so worried Mr Mantega has now turned into a shambolic retreat.

THE beauty of Twitter, the popular microblogging service, is that users have to keep it short: messages can only be 140 characters long. But companies that mine the stream of tweets for marketing and other purposes (see article in this week's issue of The Economist) get much more information. Below is a map of a tweet including all its metadata. The map was published by Raffi Krikorian, a developer at Twitter. It is 18 months old, but it is safe to say that the amount of metadata attached to a tweet has not decreased since.

The relationship between democracy and inequality between the sexes

ON SEPTEMBER 25th Saudi Arabia, the world's seventh least-democratic country according to the Economist Intelligence Unit, our sister company, announced that from 2015 it would allow women to vote and stand in municipal elections. Women have a particularly hard time in Saudi Arabia, which was the last country with some elections to deny women the vote. They must seek permission from a male guardian (often their husband or father, but sometimes their son) before they work, travel and marry, and they are not allowed to drive.