Module summary
- Read index moves as percentages, not points, and check which index is being quoted.
- A quote page combines price, spread, volume and valuation figures; each answers a different question.
- Breadth, sectors and volume show whether a move is broad or driven by a few large companies.
How to read the stock market is a skill of translation: turning a stream of numbers and headlines into a clear sense of what happened, how unusual it was, and how widely it was shared. This module works from the top down, starting with indices and ending with a single share's quote page.
Start with the index, in percent
News reports often quote index changes in points, which are hard to compare over time. Always convert to percent. With illustrative numbers: a 75-point fall in an index at 5,000 is a 1.5% move. The same 75 points on an index at 40,000 is less than 0.2%.
Also check which index is being described. The S&P 500 covers around 500 large US companies weighted by float-adjusted market value. The Dow Jones Industrial Average holds 30 companies and is weighted by share price, so a high-priced share moves it more than a larger but lower-priced one. The Nasdaq Composite includes everything listed on Nasdaq, while the Nasdaq-100 holds its largest non-financial companies. Outside the US, the FTSE 100, DAX, Nikkei 225, ASX 200, Nifty 50 and Sensex play similar roles. The DAX is a total-return index, meaning dividends are assumed to be reinvested, which makes long-run comparisons with price indices misleading.
Read breadth and sectors
A single index number hides how many companies took part. Large companies dominate market-value-weighted indices, so a handful of them can lift an index while most shares fall. Breadth measures help:
- Advancers versus decliners: how many shares rose against how many fell.
- New highs versus new lows: how many reached 52-week extremes.
- Equal-weight comparisons: how an index would have moved if every company counted equally.
Sector performance adds another layer. A day when defensive sectors rise while growth sectors fall tells a different story from a day when everything climbs together.
Anatomy of a quote page
Take an illustrative share quoted at $84.20 against a previous close of $81.00.
| Figure | Example | What it tells you |
|---|---|---|
| Change | +$3.20 (+3.95%) | Movement since the previous close |
| Bid / ask | $84.18 / $84.22 | The cost of trading right now; a wide gap signals thin liquidity |
| Volume | Shares traded today | Compare with the average; heavy volume gives a move more weight |
| Market cap | 500 million shares × $84.20 = $42.1bn | The market value of the whole company |
| P/E ratio | $84.20 ÷ $4.21 earnings per share = 20 | Price paid for each dollar of annual earnings |
| Day and 52-week range | Low to high | Where today's price sits relative to recent history |
| Dividend yield | Annual dividend ÷ price | Cash income as a share of the price |
No single figure is a verdict. A P/E of 20 can be cheap for a fast-growing company and expensive for a shrinking one. Use the numbers to frame questions, then look at the business itself. The stock market module covers ownership, orders and dividends in more detail.
Timing: before, during and after the session
US exchanges trade from 09:30 to 16:00 New York time. Before the open, index futures and pre-market trading give an early indication of sentiment, but volumes are thin and early moves often fade. Company results are usually released outside regular hours, so a share can open far from its previous close. After the close, extended-hours trading continues on a smaller scale. When reading a chart, gaps between one day's close and the next day's open usually mark these overnight events.
The market hours board shows which major exchanges are open now in your time zone.
Headlines, causes and noise
Daily market reports attach a cause to every move, but many moves have several causes or none that can be isolated. Treat "shares fell on inflation fears" as a hypothesis. Check whether the move was broad, whether volume was unusual, and whether related markets such as bonds and currencies moved the same way. Over a single day, most price changes are noise relative to the value of a business.
Reading index charts over longer periods
For anything longer than a few months, two chart settings change the picture. A logarithmic scale shows equal percentage moves as equal distances, so a fall from 2,000 to 1,000 looks the same size as a fall from 6,000 to 3,000; on a linear scale the later fall looks three times as large. And most published index levels are price indices, which exclude dividends. Over decades, reinvested dividends account for a large part of total returns, so comparing a price index with a total-return index, or with your own portfolio, can mislead. Check which version any long-run chart shows before drawing conclusions from it.
Self-check
- An index falls 300 points from 30,000. What is the percentage move?
- Why can a price-weighted index behave differently from a value-weighted one?
- What does a wide bid-ask spread tell you about a share?
Questions from readers
What does it mean when the market is up?
Usually that a major index, such as the S&P 500 or FTSE 100, closed higher than the previous day. It does not mean most shares rose; check breadth for that.
Is a high P/E ratio bad?
Not by itself. It shows investors are paying more for each unit of current earnings, often because they expect growth. Compare it with the company's history, its sector and its growth prospects.
Why did a share jump at the open?
News released outside trading hours, such as results or a takeover approach, is priced in when the market reopens, which can create a gap from the previous close.
Sources
- S&P Dow Jones Indices, index methodology documents
- Deutsche Borse, DAX index guide