What is Relative Strength vs ASPI and Why Every CSE Investor Needs It

You open your broker platform or CSE data tool and see those coloured bars stretching left and right of the zero line. That single chart is telling you which stocks are genuinely pulling ahead – and which are quietly dragging – even when the All Share Price Index (ASPI) looks almost flat. This is the relative strength metric.

In the snapshot you shared, the ASPI itself gained just +0.06% over 90 days. Yet some stocks beat that benchmark by double digits while others lagged by several percentage points. The metric simply subtracts the index return from the individual stock return. Positive bar = the stock did better than the market. Negative bar = it did worse. Simple, but extremely powerful.

Key Numbers from a Typical 90-Day Relative Strength View

• Scale runs from -6% to +18% in the example
• Red bars left of zero: underperformance vs ASPI
• Green bars right of zero: outperformance vs ASPI
• Zero line: exactly matched the ASPI return

What is the 30-Day Pairwise Correlation Matrix

Below the bars sits the correlation grid. It answers one question: when one stock moves, does the other move in the same direction, opposite direction, or not at all?

The numbers range from -1.00 (perfect opposite movement) to +1.00 (perfect same movement). The diagonal is always 1.00 because a stock is perfectly correlated with itself. The off-diagonal numbers show the relationship between different stocks over the last 30 trading days.

Quick Read of the Matrix

• Above +0.50: stocks tend to rise and fall together (high similarity)
• Between +0.20 and +0.50: moderate co-movement
• Near zero or negative: good diversification opportunity

Colour coding makes it instant – warmer tones flag stocks that behave like twins; cooler tones show true diversifiers.

How to Calculate Relative Strength Yourself

No fancy software required.

1. Take closing price of the stock today and exactly 90 trading days ago (use cse.lk historical data).
2. Stock return = (Today’s price ÷ Price 90 days ago − 1) × 100
3. Do the same for ASPI value.
4. Relative strength = Stock return − ASPI return

That is the exact length of each bar you see.

How to Calculate the Correlation Matrix

1. Download 30 days of daily closing prices for the stocks you care about.
2. Convert each day to daily return % for every stock.
3. In Excel or Google Sheets use =CORREL(range of stock A returns, range of stock B returns)
4. Repeat for every pair.

Most CSE-focused platforms now do this automatically and refresh every evening.

Why These Metrics Are Critical for Sri Lankan Investors Right Now

Sri Lanka’s economy still feels every twitch in global oil prices, DXY moves, or Fed decisions. When the rupee weakens, import costs jump and many stocks in the same sector get hit together. Relative strength quickly shows which companies are strong enough to swim against that tide. Correlation shows whether you are actually spreading risk or simply owning the same story twice.

Local entrepreneurs who keep family wealth or business cash in the market use these two tools to avoid the painful lesson of 2022 – when “diversified” portfolios still fell in unison because everything was highly correlated.

Foreign investors scanning CSE listings check the same metrics before committing capital; negative or low correlation is often what convinces them a Sri Lankan name truly adds diversification to their global book.

Impact on the Rupee and Local Portfolios

A stock showing strong positive relative strength against the ASPI tends to hold value better when the rupee comes under pressure. Its price performance already proves it can deliver returns even when the broader market is struggling with higher import bills or tighter CBSL liquidity.

On the correlation side, mixing high-correlation stocks (say two banking names both above +0.50) is like doubling your rupee exposure. Adding a low-correlation name (negative or near zero) can reduce overall portfolio volatility without sacrificing expected return.

Strategic Outlook

The CSE has come a long way since the dark days of low liquidity. Daily turnover, weekly CBSL reports, and monthly fiscal numbers now feed directly into these clean, visual metrics. Professionals who check relative strength every Friday and scan the 30-day correlation grid before adding any new position stay ahead of both local sentiment shifts and global spillovers.

Keep the periods flexible – 30 days for tactical moves, 90 days for confirming real trends. The numbers never replace fundamental research, but they remove the biggest source of regret in any market: buying something that looked cheap but was simply moving with the crowd all along. Use them consistently and your CSE portfolio will start behaving less like the index – and more like a deliberate, well-constructed engine for Sri Lankan wealth creation.