In this guide
What NASI measures
The NSE All Share Index tracks the total market value of the ordinary shares listed on the Main Investment Market Segment and the Alternative Investment Market Segment of the Nairobi Securities Exchange. It started at 100 on 24 December 2007, the last trading day of that year (NSE ground rules, section 4). When NASI reads 120, the market as a whole is worth 20 % more than on that day (not counting dividends). It is published once a day after the 3 pm close, which is also when the figure on KenyaStocks updates; the NASI page shows today's level, the advancers and decliners behind it, and the history we hold.
Why the big companies steer it
NASI is market-cap weighted: each company counts in proportion to its total value (share price × shares in issue). Safaricom alone is worth more than a third of the whole exchange, and the large banks (Equity, KCB, Co-operative, Absa, Standard Chartered, NCBA, Stanbic) make up much of the rest. So a 2 % move in Safaricom shifts NASI by roughly 0.7 %, while a 10 % jump in a small company barely registers.
- A day when NASI is up but most shares are down usually means Safaricom or a big bank rose.
- The market summary on the home page shows advancers and decliners alongside NASI for exactly this reason.
- The Sectors tiles show the same idea at sector level: Telecommunication is one company.
What actually moves it
Company results and dividends
Half-year and full-year results, and the dividend announced with them, are the biggest single-company moves. Bank results cluster in March and August.
Interest rates
When Treasury bill yields rise, some money leaves shares for government paper and NASI tends to drift down; when yields fall the reverse happens.
The shilling and foreign investors
Foreign funds hold a large share of Safaricom and the big banks. A weaker shilling or a risk-off week abroad shows up as selling in those names.
Policy and the budget
Tax changes in the Finance Bill, CBK rate decisions and regulation affecting a whole sector (banking, telecoms, energy) move groups of shares at once.
NASI, NSE 20 and NSE 25
| Index | What is in it | How it is weighted | Use it for |
|---|---|---|---|
| NASI | Ordinary shares on the main and alternative segments | Market value | The market as a whole |
| NSE 20 | 20 large, liquid blue chips chosen by the exchange | Geometric mean of prices (each share counts equally) | The traditional headline figure; moves less with Safaricom |
| NSE 25 | 25 large, liquid companies | Market value | A tradeable large-cap benchmark |
KenyaStocks shows NASI because it covers every company on the site. NSE 20 and NSE 25 are not shown yet.
How to read a day's move
A move of 0.5 % in a day is ordinary; 2 % is a big day and usually has one cause you can find in the news. Look at three things together: the NASI change, how many shares rose versus fell, and which companies are in the movers list. Broad advances with many gainers are healthier than a rise carried by one share.
Because NASI is price-only, it understates what a long-term investor actually earned: dividends are not in the index.
Sources
- Nairobi Securities Exchange: Ground rules for the NSE All Share Index (PDF)
- Capital Markets Authority: the regulator of the exchange
Sources checked · General information, not investment advice.
