The Money Maze TMM Nº 022

Market Breadth, Index Weighting and Free Float Explained

Length: 6 min

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Market breadth, index weighting and free float explained for JSE investors: why a few giants can drag the Top 40, and why thin free float means big swings.

Show notes

Three terms that sound like an MBA exam but quietly control what you see on your investment app: market breadth, index weighting and free float. Here’s what they mean, and why your Top 40 ETF sometimes behaves like a fan club for a few big names.

By The Money Maze | Listen to the episode: Spotify

“The JSE closed 2% higher today.” Sounds like a party. But was everyone dancing, or were three okes carrying the whole dance floor? That’s the question these three concepts answer.

What is market breadth?

Market breadth measures how many shares are joining in when the market moves.

The basic version compares advancing shares with declining shares. If 35 of the Top 40 are up, breadth is strong. If only five are up and 35 are sulking in the red, breadth is weak, even if the index closed higher because the five winners were giants.

It’s a braai where one guy brought steak and everyone else brought pap. Technically there’s food. It’s not balanced.

Why breadth matters

Breadth tells you whether a rally has legs. A broad rally, with most shares rising, suggests investors are confident across the market. A narrow rally, carried by a few heavyweights, is more fragile: if those few stumble, there’s nothing underneath.

Common breadth measures:

  • Advance-decline line: a running total of advancing minus declining shares.
  • New highs vs new lows: how many shares hit 52-week highs versus lows.
  • Percentage above a moving average: how many shares trade above, say, their 200-day average.

Breadth on the JSE is a special case

The JSE has a quirk that makes breadth extra useful. Many of its biggest companies earn most of their money offshore: global internet stakes, luxury goods, international mining. Meanwhile, many smaller companies depend on the South African economy. So the Top 40 can rise because of Chinese tech or gold prices while local banks, retailers and builders struggle. Breadth helps you separate “global giants had a good day” from “South Africa Inc. had a good day”. They’re very different stories, and they matter differently depending on what you own.

What is index weighting?

Index weighting decides how much each share influences the index. Most major indices, including the FTSE/JSE Top 40, use market-cap weighting adjusted for free float. Bigger companies carry more weight.

Picture a tug-of-war team with Dwayne “The Rock” Johnson and nine Grade 5 prefects. Guess who’s doing the pulling.

On the JSE, a handful of giants such as Naspers, Prosus, the big miners and Richemont have carried very large weights at different times. When those few move, the index moves, whatever the other 30-odd companies are doing. That’s why capped indices exist, putting a ceiling on any single share’s weight.

Other approaches:

  • Equal weighting: everyone gets the same size chop, even the guy who only brought ice.
  • Price weighting: higher share price, more influence. Old-school, like the US Dow. Price doesn’t equal size, which is why it’s rare.
  • Fundamental weighting: based on earnings, dividends or other measures.

If you own a market-cap-weighted Top 40 ETF, you’re making a big bet on the biggest names. Check the top holdings so you’re not surprised.

What is free float?

Free float is the share of a company’s stock that’s actually available to trade. Not all shares in issue are on the market. Some are held by founders, controlling shareholders, governments or strategic partners who don’t plan to sell.

Example: a company has 1 billion shares. The founder holds 400 million and a strategic partner holds 200 million. The free float is the remaining 400 million, or 40%.

Why free float matters

  • Index weight: FTSE/JSE indices weight companies by their free-float market value, not total value. A giant with a small free float gets a smaller weight than its size suggests. Free float figures are updated at the quarterly reviews.
  • Volatility: with fewer shares available, small trades can move the price a lot. When a small-cap swings like a DJ at a wedding after too many tequilas, check the free float.
  • Liquidity: thin free float often means wider bid-offer spreads, so you pay more to get in and out.

Putting it together: a real-world reading

Imagine the Top 40 rises 1.5% in a day. You check breadth: only 12 of 40 shares rose. Two heavily weighted shares jumped 5% on offshore news. The rest drifted lower.

What does that tell you? The headline number came from a few giants, not from broad confidence in South African companies. If you own a Top 40 tracker, you benefited. If you own mid-caps or local industrials, your portfolio may have gone backwards on a “good” day.

Why you should care

  • Breadth: tells you whether a rally is broad or top-heavy.
  • Weighting: explains why some shares dominate your ETF.
  • Free float: tells you how liquid a share is and whether you’re walking into a volatility party.

Stokvel Starter Pack

  • Market breadth: how many shares join a market move.
  • Advance-decline line: a running count of risers minus fallers.
  • Market-cap weighting: bigger companies count more.
  • Capped index: a ceiling on any single share’s weight.
  • Free float: shares actually available to trade.
  • Thin free float: fewer shares trading, bigger price swings.

Takeaway: Don’t judge the market by the headline number alone. Check who did the heavy lifting, how much they weigh, and how many shares are really floating.

Want the full braai version? Listen on Spotify. And if you’d like the Maze in your inbox, join the free Maze Mail list.

More from The Money Maze

Sources

  1. FTSE/JSE Africa Index Series ground rules v9.1, JSE and FTSE Russell.
  2. FTSE/JSE Africa Index Series ground rules v8.8, JSE and FTSE Russell, Mar 2025.

This is not financial advice.

Transcript

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0:00 Welcome to another episode of The Money Monies, the podcast for South African retail investors who want to stop feeling like they're drowning in jargon and start navigating the markets like someone who actually knows what they're doing. I'm your host, Jay, and today I'm coming to you from Ethiopia, where we unpacking 3 concepts that sound like they belong in a fancy MBA exam but actually control how the stock market flexes its muscles.

0:25 Market breadth, index weighing and free float. By the end of this episode, you'll know by these matter and how they influence what you see on your investment app. Now pour yourself a strong cup of coffee, because this one's going to be lucky, informative, and unlike the usual family meeting promises I'll actually deliver. Let's start with market breadth. This is basically a measure of how many stocks are playing around in the market moves.

0:53 Think of it like this, if the Jazz Top 40 is up 2%, does that mean everyone's happy? Or is it just a few heavyweights pulling the entire index up, like that one Okino office who does all the work while the rest of the team plays Candy Crush? Market breadth looks at the number of advancing shares versus declining stocks. So if 35 out of 40 stocks in the J's Top 40 are up, that's strong breadth.

1:18 If only 5 are up and the other 35 are sulking in the red, that's weak breadth, even if the index itself is positive. It's like being at a BRA where only one guy brought stake and everyone else has PUP. Technically there's food, but it's not balanced. So why does this matter? Because Britt tells you if a rally has legs or if it's just built on the back of a few big names.

1:42 If not, person processes are pumping while everyone else is sleeping. You've got a very top heavy market. That's like balancing your whole financial future on a dodgy pyramid scheme WhatsApp group. Not ideal. Now we look at index weighing. This is where things get spicy because index weighing determines how much each stock influences the overall index movement. Most major indices, like the JSC Top 40 use market cap weighting. That means the bigger the company's market cap, the more weighted carries.

2:14 So if Naspers sneezes, the entire JC catches a flu picture tug of war team where one guy is Dwayne The Rock Johnson and the other nine are Grade 5 reflects. Who do you think's going to do the pulling? That's the market cap weighting for you. Other types of weighing include equal weighting. Every stock just the same weight, like giving everyone the same size chop at the Bri, even the guy who only brought a packet of ice.

2:41 Price waiting. The higher the share price, the more influence. This is old school, I think Dow Jones, but hardly anyone uses it today because price doesn't always equal size. Then you have fundamental weighting. This is based on metrics like earnings and dividends, which sounds great in theory, but in practice it's like letting your mother-in-law pick your fantasy football team. A little bit risky for US retail investors. This matters because your ETF's performance depends on how the index is weighted.

3:11 If you own a JSE Top 40 ETF, you're basically betting heavily on Nash Process and Richmond because they dominate the waiting. Now, finally, let's talk about free float. This one sounds like a lacquer summer pool party, but it's actually about how many shares are freely available for trading on the market. Not all shares you see in a company's total count are available to you. Some are locked up by insiders, governments or even long term investors who never sell.

3:40 Free float is what's left for the rest of us pledged to buy and sell. For example, if a company has 1 billion shares outstanding, but 400 million are held by the founder and another 200 million by a government pension fund, then the free float is 400 million shares. So why does this matter? Because low free float can make a stock more volatile than a Springbok fan at the Rugby World Cup. With fewer is available, even small trades can move the price dramatically.

4:10 So when you see a small cap stock swing like a DJ at a wedding after too many tequilas, check that free float. Chances are it's still as picking Pi's budget after paying suppliers. So why should you care about all of this? Market breadth helps you gauge if a rally is broad based or just a couple of big names doing all the heavy lifting. Index Whiting explains why some stocks dominate ETFs and indices, so you're not shocked when your Top 40 ETF performs like a nice person.

4:37 Fan club Freeflow tells you how liquid stock is and whether you're walking to a volatile party uninvited. Let's do a quick real world example for you. Take the JSE Top 40 last passion process together can make up more than 20% of the index. So if they rally the Top 40 looks like a year or even if most of the other shares are still snoozing, that's poor market breadth.

5:01 Was a heavy market cap weighting buyers. Add in a stock with a low free float like an obscure mining junior, and suddenly you've got a recipe for chaos. One big buy order and the price moves faster than the Dogecoin in 2021. Now it's time for your stock fell. Start to back off stock lingo for this episode 22. Market breadth is how many stocks are actually joining the party when the market moves.

5:29 More dancers equals healthier market index waiting. Who's really pulling the rope in the index spoiler? It's the big guys. Free float is the shares that are actually up for grabs. The smaller the float, the Wilder the right. Then there you have it folks, another jargon jungle conquered. And while my jokes may have more float than some Jays you small caps, Please remember this is not financial advice. Please do your own research and speak to a licensed advisor and I'll catch you next time on the Money Maize when we have a look at headline earnings versus core earnings write offs and adjusted metrics.

The JSE stories worth knowing about, explained like a mate would at the braai. No hot tips, no spam.

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