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Les indices MASI, MSI 20 et MASI ESG : que mesurent-ils ?

مؤشرات MASI وMSI 20 وMASI ESG: ماذا تقيس؟

MASI, MSI 20 and MASI ESG indices: what do they measure?

What is a stock index?

An index is a basket of stocks whose average performance is tracked, weighted by each component’s size. It expresses a market or sector trend in a single number. When the MASI rises 1%, listed stocks advance on average — but not equally: large caps pull the index more than small ones.

The MASI: barometer of the whole market

The MASI (Moroccan All Shares Index) includes all stocks listed on the Casablanca Stock Exchange. It is calculated on a free-float market-cap basis: only the portion of shares actually available to trade (the float) counts in the weighting. A controlling shareholder holding 60% of capital does not move the index with their sales — the float does.

Who moves the MASI? — Top components

Three stocks concentrate a major share of the MASI. Here are their characteristics on Casabourse (June 2026):

Rank Stock Market cap (~) Indicative MASI weight Volume/day (~) Index impact
1 Attijariwafa Bank (ATW) ~146 bn MAD ~18–20% ~48,104 Largest cap: a 2% rise in ATW alone can add ~0.35 pt to the MASI
2 Maroc Telecom (IAM) ~80 bn MAD ~12–14% ~44,070 Defensive name: stabilises the MASI in stress, but also dampens rallies
3 BCP ~49 bn MAD ~7–9% ~8,130 Morocco’s 2nd bank: correlated to banking and the credit cycle
Top 3 combined ~275 bn MAD ~38–43% Nearly half the MASI depends on 3 stocks alone

Indicative weights based on free-float market cap (Casabourse, June 2026). Exact weights are recalculated periodically by the BVC.

Concept: free-float market-cap weighting

Think of the MASI as a scale: the bigger and more liquid a company is (high float), the heavier it weighs. Simplified formula:

Weight = (Price × Free-float shares) / Total free-float market cap of the market

Consequences for you:

  • If you hold only ATW, IAM and BCP, your portfolio mirrors the MASI — you are not truly diversified.
  • A micro-cap that doubles barely moves the MASI.
  • The MASI can rise while your favourite stock falls (and vice versa).

The MSI 20: the 20 locomotives

The MSI 20 groups the 20 largest and most liquid names. ATW, IAM and BCP naturally feature, along with Label Vie, LafargeHolcim, Cosumar, etc. More concentrated than the MASI, it reflects the behaviour of the “heavyweights” investors trade most easily.

Sector indices and MASI ESG

The BVC also publishes sector indices (banks, telecoms, real estate…) and the MASI ESG (companies best rated on environment, social and governance). Comparing ATW performance to the bank index, or IAM to telecoms, is a useful analysis habit — available on Casabourse.

What are indices for as a beginner?

  1. Barometer: is the MASI up or down? You situate the general context before buying.
  2. Benchmark: is your portfolio doing better or worse than the MASI over 6 months?
  3. Diversification: if you hold only the 3 largest caps, you are not diversified despite 3 different names.

Performance zoom — MASI vs 4 components (52 weeks)

Understanding the MASI also means seeing who pulls the index over a year. Indicative Casabourse variations (June 2025 → June 2026):

Index / stock ~52-week change Indic. MASI weight Reading
MASI +12.4% 100% Overall market barometer
ATW +47.2% ~18–20% Outperformed the index — pulled the MASI up
IAM −8.1% ~12–14% Underperformed — defensive drag on the index
BCP +22.6% ~7–9% Positive contribution, less than ATW
Disway +5.3% < 0.5% Micro weight: your gain barely affects the MASI

Indicative Casabourse figures. A 100% ATW portfolio would have beaten the MASI by a wide margin; a 100% IAM portfolio would have underperformed despite “being in the market”.

Practical exercise on the BVC

Open the Casabourse comparator and compare ATW, IAM and BCP: market cap, 52-week change, dividend yield. Estimate mentally: if ATW is ~20% of the MASI and rises 3%, what approximate impact on the index? Then add a 4th name outside the top 3 (e.g. Disway) and observe the weight difference — that is real diversification.

Key takeaways

  • The MASI covers the whole market, weighted by free-float market cap.
  • ATW (~20%), IAM (~13%), BCP (~8%): the top 3 weighs ~40% of the index.
  • The MSI 20 is more concentrated on large liquid names.
  • Comparing your portfolio to the MASI = knowing if you beat the market.
  • Casabourse and the comparator let you visualise market caps and relative weights.

Self-check

  1. What does the MASI include and how is it weighted?
  2. What are the three largest MASI weights on Casabourse?
  3. Why does the float matter in index calculation?
  4. How does the MSI 20 differ from the MASI?
  5. How do you use the MASI as a benchmark for your portfolio?