The numbers of the year 2013
What were the most significant numbers of 2013? Several experts name their favourites, and explain why.
David Spiegelhalter, Cambridge University: My number of the year is 7.3. This is the average response given by about 165,000 people when the UK's Office for National Statistics asked them on a scale of 0-10 how happy they were the day before.
It's about the same as last year. About 15% were completely manic and said 10. And 1% were really miserable and said zero. Only 10% said four or less.
The question: Are you satisfied with your life? got an average of 7.5 - higher if people were married, lower if they were unemployed, and slightly higher for females. The most miserable age is 45-54 (I remember it very well) and the happiest is 65-79 (I can't wait).
Those smug Danes said 8.4 even in spite of the gloomy crime dramas they watch, while Bulgarians said 5.5, the lowest in the European Union. That means that if the happiest Bulgarians come to the UK the average happiness in both countries would go down.
Linda Yueh, BBC chief business correspondent: My number of the year is 95 because it's the eye-catching number of the economic recovery, five years on from the worst crash in a century.
Income inequality has risen sharply during the recovery. In the US, the top 1% of income earners have captured 95% of the income gained since 2009. A study at the University of California at Berkeley found the top 1% incomes grew by 31.4% while the bottom 99% increased by only 0.4%. So few people have seen their incomes rise, it's really hard to see the recovery as broad-based.
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This was the gist of a disagreement between two Nobel prize-winning economists. Joseph Stiglitz sees this inequality as a reason why the recovery is so slow. Paul Krugman, on the other hand, thinks that is too simple an explanation.
This recovery has been supported by lots of easy money instead of more government spending and that easy money has helped stock markets hit record highs. If that's the main source of growth - as in stock prices going up - then maybe it's not too surprising that the richest, who own more stocks than the poor, see their incomes go up.
That's not enough to support the rest of the economy and that's one of the reasons why economies still have not recovered - for instance in Britain - to pre-crisis levels.
Simon Singh, author: My number of the year is 22 and it relates to a problem called pancake sorting, created by Jacob Goodman, who was 80 this year.
Imagine you have a stack of pancakes of different sizes and in the wrong order and you want to get them into the right order - say, with the smallest at the top and the largest at the bottom. You can stick a spatula anywhere in the stack and flip over all the pancakes above that point.
If you have two pancakes and they're in the wrong order then the "pancake number" is one, because you only need one flip to swap them over. For three pancakes, the maximum number of flips required is three.
You can work out the pancake number for various numbers of pancakes, and the number for 19 pancakes is 22. That's my number of the year because mathematicians have not been able to calculate the pancake number for 20 pancakes.
By the way, the only research paper that Bill Gates ever wrote was on the subject of pancake numbers.
Dr Pippa Malmgren, Principalis Asset Management: 73 is the periodic table number for an element few people have ever heard of, tantalum. We're incredibly dependent on this rare earth metal. It's essential for all telecommunications, and lots of defence equipment - and your mobile phone won't work without it.
Tantalum serves as a reminder that in the world economy lots of the most important things that we need are actually very limited in their supply. You assume that if you need something like tantalum you just get it. Well, guess what? We don't have enough engineers, including mining engineers, and we probably won't for some years to come until we fix and redress this balance.
For the last 25 years if you had any maths skills you went into finance because that career paid the most. It means we've also got a global shortage of engineers right now.
This year is really interesting because it's the first year that the graduates of the Colorado School of Mines, America's best engineering school, will be paid more than Harvard Business School graduates thus enticing young people with maths skills to go back into the real economy, which is a great thing.
Dr Hannah Fry, University College London: My number of the year is 51 and this comes from the UK's 2011 Census, from which a lot of data has been released this year.
One astonishing statistic caught my attention - apparently 51 people in the UK were born in Antarctica... despite there only being 11 people ever recorded as being born there.
This probably suggests that there are 51 people in the UK who have a particular sense of humour.
Looking at some of the other numbers in the 2001 Census, 390,127 people put down their religion as Jedi Knight but that joke has now got a bit old and Jedi Knights have been overtaken by Buddhism and Judaism.
But another joke has crept in. There are the Free Thinkers - 513 of them.
We shouldn't be too worried about these answers putting the census into disrepute. These are small numbers of amusing outliers.
Paul Lewis, presenter of Moneybox, on BBC Radio: My number is 33.86 - that's the number of petaflops achieved in 2013 by the new holder of the title "world's fastest computer".
Peta is a million billion - that's 10 to the power of 15. A flop is one floating point operation per second. Think of it as multiplying two really long numbers together in a second - that is a flop. So a petaflop computer can do a million billion long multiplications every second, and get them right.
When the list of fastest computers was published in June, China's new Tianhe-2 computer went straight in at number one. It achieved 33.86 petaflops, which was nearly twice as fast as the runner up, a computer called Titan in the US Department of Energy. It was still the fastest in the latest list published in November.
It's doing 33,860 million billion sums every second. Computing records seldom last long and two months before China's great leap forward the first one-petaflop computer, which was king in 2008, was decommissioned for being too slow.
When the next list comes out Tianhe-2 may beat itself. Its theoretical top speed is more than 50 petaflops but even that record may soon go because the geeks are betting on a 1 exoflop machine by 2017. That's a billion sums every billionth of a second.
On a tablet? Read 10 of the best Magazine stories from 2013 here