Learn the stock market › Why does a stock move? › Lesson 3 of 9

Why is the stock market down?

Short answerA market falls when something touches almost every company at once: interest rates, a weaker economy, worry about the world or falls on other exchanges. Many people sell at the same time, and few want to buy at yesterday's price. On days when Stockholm has fallen at least 2%, the median share of the largest companies falling has been 96%.

A market rarely falls alone

Since November 2008, OMX Stockholm 30, the index of the 30 most traded Stockholm stocks, has fallen at least 2% on 207 of 4,506 trading days. These five were the largest.

Day	OMX Stockholm 30	Companies that fell
Mar 12, 2020	−10.6%	30 of 30
Jun 27, 2016	−8.4%	25 of 26
Aug 18, 2011	−6.7%	24 of 24
Dec 1, 2008	−5.4%	23 of 24
Mar 9, 2020	−5.3%	30 of 30

An index is an average of its companies, so it only falls far when many of them fall. On such days, what decides is rarely something inside one company.

The largest fall came on Mar 12, 2020: −10.6%. The companies are the 30 in the index today, as far back as they have prices.

What moves the whole market

Interest rates. Higher rates make borrowing dearer and saving without risk more attractive. See the lesson on rates.

The economy. If people and companies are expected to buy less, almost every company is expected to earn less.

Worry. Wars, political decisions and pandemics make the future harder to judge, so buyers pay less for the same profits.

Other exchanges. When New York falls in the evening after Stockholm has closed, the answer often comes when Stockholm opens the next morning.

The latest example

This is what we wrote about the Stockholm market on the latest day we have reviewed. The text changes every evening.

Friday, November 6, 2026
OMX Stockholm 30 Index fell after a US sell-off. Stockholm's market fell clearly in the last session, with 28 of its 30 companies declining and only 2 rising. The biggest drags were AstraZeneca, Investor and Volvo, which all fell in line with the broader market. The market-wide drop followed a very sharp fall in the S&P 500 and Nasdaq in the last US session, which likely weighed on sentiment. Over the last five trading days, the index was roughly unchanged, so it held up better than the US market.

How long and deep the truly large crashes have been is in the study of every crash since 1928. Whether the market does worse in some halves of the year is tested in the Sell in May study.

Test yourself

Every large company in an index falls on the same day. What is the most likely explanation?

How did it go today? How the market did.