There are always at least two stories you can tell from an economic number. Economies are complicated places, there are many moving parts, so any one number can have more than one explanation.
It's also true that there are many economic models that we can use at any one time. The art of economics is to select the correct model to explain -- or investigate -- the particular thing we are interested in at the moment.
As a general rule but not a perfect one, all economic models explain something usefully, and none of them explain everything. Model selection is therefore everything.
So, a writer for this newspaper says that even as the economy is growing, deposits in banks are not growing. We could, as the assumption is made, think that this is a bad thing.
People have less to save -- less to deposit -- after paying for life. That's a perfectly respectable, entirely sensible, reaction to the number. But is it the correct one?
To walk away from this specific to something more general. Thomas Piketty, the French economist, has been complaining loudly for years that the ratio of capital or wealth to GDP has been rising. He then says this is going to send us all back to Jane Austen days where inheritance will be everything and no one will be able to work their way up.
Therefore, tax rich people more. Just as an individual thing, I come from Bath and used to walk past Jane Austen's house regularly -- in fact, used to work next door to it. I've even worked -- as a teenage waiter -- in the ballroom she used to attend and in which nearly all of the movies are filmed.
Back to Jane Austen days doesn't scare me all that much. Just to give out too much personal information, the opening scenes of Bridgerton (which is not, not, Jane Austen!) shows the outside of my apartment.
It is possible to run with the Piketty idea. It's also possible to explain the same number another way.
Wealth, capital, is the stock of society. GDP is the income we gain from that. So, if the wealth to GDP ratio is rising, then we're becoming less efficient at turning our assets into income.
Explaining the same number that way leads to another conclusion: We should have less bureaucracy, less government, so that we increase efficiency. The same number that Piketty is using but the different model leads to an entirely different solution. Which is right? Well, that's the art of economics.
One of the odd truths of economic numbers is that when we measure by wealth -- wealth, not income -- there are more poor people in the US, and they are poorer, than there are in Bangladesh. This is because the US banking system -- the whole financial system -- allows people with no assets to borrow.
So, people can have negative wealth -- a student with college loans, someone with no assets, a job and a credit card balance -- and so that's just true. An efficient financial system can mean that because people can borrow then there are more people with negative wealth.
Another odd number. The Federal Reserve asks a regular question: If you had a $400 bill -- the heating system needed repair, say, -- then how would you pay for it? 37% say they wouldn't use cash, they would borrow.
OK, we can think of this in two ways. One is that this is appalling, 37% of US households don't have enough cash to pay a $400 emergency bill. The other is that the US financial system is so efficient that people who might face a $400 emergency bill don't need to save cash to maybe pay it. If it does happen -- the emergency -- then they can borrow and pay that back later.
Which model we use, which story we tell about the number, makes a difference.
Deposits in Bangladeshi banks are falling? Is that because Bangladeshi households have less money to save after meeting expenses? Or is that because the financial system is getting better so that Bangladeshi households need to have less cash savings because they can now borrow if they need to?
I'd not even pretend to know, let alone insist, what is the correct explanation for household deposit savings falling in Bangladesh. But I do insist that which explanation is true matters enormously. Which model, which explanation, is the very heart of the whole subject of economics. Exactly what makes it so fun and so annoying in fact.
Tim Worstall is a senior fellow at the Adam Smith Institute in London.