Now, there is a reason not to worry about this. It’s that our deficit is the counterpart of foreigners being net savers: Europeans and Asians want to save, which means that someone must borrow. That someone is us. And we can do so at low interest rates.
This, though, is exactly the same thinking which tells us not to worry about government borrowing. It too is the counterpart to savings (by companies and foreigner) and it too can be financed at low interest rates.
Instead, there's another reason not to worry about the current account deficit. It's that the current account is only a very partial measure of changes in the UK's balance sheet. For example, if we buy cars from overseas and sell a house to a foreigner to finance it, the imported cars show up as a current account debit, but the house isn't a current account credit; it is measured as a capital account inflow. Such transactions will thus create a current account deficit, even though it is arguable whether there is anything troubling about this exchange.
Or take another example. If you borrow from overseas to buy a foreign asset which rises in price, your interest payments will appear as a current account debit, but your capital gain will not. A perfectly sensible investment will therefore generate a deficit.
This is no mere theoretical possibility. It is exactly what has happened. Since the end of 2012 the UK’s net overseas liabilities have actually fallen from £239.1bn to £21.2bn thanks in part to a rise in the value of our overseas equity holdings.
Sadly, though, all this might be a little complacent. The current account deficit might not necessarily be a problem in itself. But it is a worry because it could be a sign of a fundamental problem with the economy - that our exports aren’t doing as well as they should.
According to the OECD the volume of world trade in goods and services has grown by 29.5 per cent since it troughed in the second quarter of 2009. However, during this period the volume of UK exports of goods and services has grown by only 15.1 per cent - barely half the growth of world trade. This is despite the fact that sterling’s big fall at the end of 2008 should have given us a competitive advantage.
Granted, some of this shortfall is because of geography; the world’s best-growing markets have been far-off lands to whom we have traditionally exported little. But not all of it is; UK exports to the US have fallen in the past 12 months, even though the economy there has grown.
In this sense, the deficit is alerting us to the fact that the supply of UK goods hasn’t kept pace with potential demand. Whether this is because of a lack of finance, lack of confidence or entrepreneurial spirits or something else is another matter - but I suspect it’s not unrelated to the stagnation in labour productivity.
Whatever the cause of it, the fact is that we have here a supply-side problem. And not just on the export side. Since 2009Q2, the volume of imports has risen by 17.1 per cent while domestic spending has grown just 6.1 per cent. This too is a sign that UK output hasn’t kept pace with demand.
Of course, if supply can’t increase as demand does then we face years of slow growth - and perhaps inflation too if supply-constrained firms raise their prices.
Either would be bad for equity investors. And history warns us of this. Since 1986, there’s been a significant positive correlation between the current account balance and All-Share returns in the following three years, with big deficits pointing to below-average returns.
Now, this doesn't guarantee bad times for shares. One possibility - which the OBR expects to happen - is that demand growth picks up in overseas markets which would boost our exports even if these do continue to lag behind that demand growth. Another possibility is that the supply constraint on exports and import substitutes might ease a little; a good reason for optimism here is that banks might step up their lending - although Bank of England figures this week showed that this is not happening yet.
What is clear, though, is that unless something changes the big current account deficit is indeed a cause for concern.
