Major tech firms watched their stock values slide after a post-US-midterms sell-off, with the global dip blamed on expectations of a slowdown in AI development - a slowdown that arrives, awkwardly, right after years of sharp rises. So the market has discovered that what goes up on the promise of artificial intelligence can also come down on the promise of artificial intelligence.
As companies grow, they may issue shares, and many of the UK's largest companies have shares bought and sold on the London Stock Exchange. Their collective performance gets quoted amid a blizzard of numbers that may feel confusing and irrelevant. Booms and falls make the news, but rarely does anyone mention the FTSE 100 during a coffee with friends. Yet there are good reasons this performance affects your life and finances.
Many people's first reaction to "the markets" is that they are not directly affected, because they do not invest money. Yet millions of people have a pension - private or through work - whose savings, in what is known as a defined contribution pension, are invested by pension schemes. The value of that pot is influenced by these investments. Pension savers mostly let experts choose where to put the money to help it grow, and widespread share-price falls are likely to be bad news for them. Hundreds of billions of pounds are currently held in defined contribution pensions.
So big rises or falls can affect your pension, but the advice is to remember that pension savings, like any investments, are usually a long-term bet. Experts say investors have always had to ride economic shocks, and that investments by definition require a long-term outlook and strategy. They urge people not to panic or make knee-jerk decisions in such circumstances. Some people have a pension promising a specific value depending on their salary; others have no pension at all.
Millions have been automatically enrolled into a pension and may not really have noticed. Those schemes see employers divert wages into a pension and contribute some money themselves, while the government adds a little in tax relief. In every case, the value of these savings is affected by investment performance. So "the markets" matter - maybe not as much as everyday wages, but for future pensions.
Timing is more critical for those at retirement age, as that may be when a retiree uses their pot to buy a retirement income, or annuity. The bigger the pot, the more income they get in retirement. As you approach retirement age, pots tend to be moved to less risky investments such as government bonds, which can do better when stock markets fall. Anyone with a pot invested and taking an income will again see their investment go up and down with the markets - which could mean getting less than expected if they cash in too much after a fall, making it important to plan how to make up any shortfall, experts say. Higher interest rates, however, tend to mean better rates on annuities, and there is a chance of more rate rises in the UK by the Bank of England.
If share prices fall for an extended period, that could affect jobs. Investors in a company expect a return on that investment; when it falls for a while, they expect the business to address issues, for example by cutting costs - and therefore jobs. There is a huge element of the unknown here, though: companies consider lots of factors when making decisions on investment and employment.
In purely investment terms, lower share prices can offer an opportunity to buy, in the hope they recover and rise over the long term. Many people will do this initially through a stocks and shares Individual Savings Account (Isa). It is worth noting, however, that the sell-off in tech stocks in particular came after big rises, so long-term investors are still likely to have seen gains. Experts and regulators are at pains to point out that investments can go down as well as up, and urge people not to put everything into one investment but to diversify.
Some people invest in what are known as tracker funds, which go up and down in line with a certain index, such as the FTSE 100. If the index falls, so does the value of their investments, and vice versa. One advantage of these funds is that they often cost relatively little to sign up to.
Yes, millions of people do invest, but experts stress a long-term strategy is required to ride out short-term falls. It is also important to hold cash savings so unexpected expenses - like a replacement boiler - can be covered. The government is keen to get people in the UK to invest more, partly because it says that will help UK economic growth and partly because investing is much more popular among individuals in the US and some parts of Europe. It backed an advertising campaign to encourage people to invest, funded by some of the UK's biggest financial services firms. But the choice of "Savvy the Squirrel" to front the campaign has raised some eyebrows. Some question whether the push could get anywhere close to the success of the Tell Sid adverts of the 1980s, which encouraged people to invest in the newly privatised British Gas.
When we see big shifts in stock markets there can also be fluctuations in currencies and exchange rates. As a result, prices could go up - but could also go down. Upheaval to economies across the world, to oil prices and so on, has a big impact on what we pay at home for goods and services, so there are lots of factors in play.
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Clarification 19 December: This article was amended to provide more context around how companies issue shares.