Bank and Commodity Stocks Are Falling: A Diversification Lesson for Passive Investors

When the IHSG (Indonesia’s main stock index) drops sharply, a few sectors usually get blamed. Big banks weaken. Commodity stocks fall. Foreign investors pull money out. Coal or CPO prices move. Economic headlines add more pressure.

For passive investors, those sector details matter, but not as a signal to guess which stocks will bounce first. The deeper lesson is simpler: the Indonesian stock market has concentration risk.

When several large sectors fall at the same time, the index feels heavy too.

The IHSG is not the whole Indonesian economy

A lot of new investors assume that buying an IHSG index fund means they have already bought “the whole Indonesian economy” in a balanced way. In reality, it does not work like that.

A stock index only contains companies listed on the exchange. The weights are not equal either. Large companies have much more influence than small ones. If big banks, telecoms, energy, or commodity companies are under pressure, the index can struggle even when many other businesses are doing just fine.

That is not a flaw. That is simply how an index works.

But investors need to stay aware of what they are buying: an Indonesian index still means taking risks that are specific to the Indonesian market. The article on Indonesian stock market risk goes into more detail.

Why do big banks matter so much?

Large banks have huge market capitalizations and high liquidity. Many institutional investors, both foreign and local, treat them as core holdings. Because of that, when sentiment around the banking sector gets worse, the impact on the index can be significant.

The banking sector is sensitive to a few things:

• credit quality and the risk of rising bad loans;
• interest rates and net interest margins;
• economic growth;
• household purchasing power;
• foreign investor flows.

If the economy slows down, the market usually starts asking: will credit growth slow too? Will borrowers have a harder time paying? Can bank profits still keep rising?

Those are fair questions. But passive investors do not need to answer them by buying and selling bank stocks every week.

Why do commodities make the market more cyclical?

Indonesia has many companies tied to commodities: coal, palm oil, metals, energy, and the businesses around them. This sector can generate big gains when commodity prices rise. But when prices fall, demand weakens, or regulations change, earnings can come under pressure too.

Commodity stocks often move in cycles. Good times can look very good. Bad times can feel brutal.

If your portfolio is too heavy in individual commodity stocks, that risk gets even bigger. Index funds help spread the risk across many stocks, but they do not remove the reality that the Indonesian market still has meaningful commodity exposure.

Do not suddenly turn into a stock picker

A common mistake when a big sector falls is feeling like you now have to pick the next winner immediately.

Banks fall, so you switch to consumer stocks. Commodities fall, so you switch to technology. The Rupiah weakens, so you switch to exporters. Interest rates rise, so you switch to deposits. Every week seems to bring a new story.

The problem is that sector rotation looks easy only after it already happens. It is hard to do in advance.

Passive investors choose a different path: admit that they do not know which sector will win next month, then build a portfolio that still makes sense across many scenarios.

Diversification does not just mean owning many Indonesian stocks

Owning 30 Indonesian stocks does not automatically mean you are diversified if all of them are still sensitive to the domestic economy, the Rupiah, interest rates, and foreign capital flows.

Stronger diversification usually works across several dimensions:

1. Across asset classes

Mix stocks with more stable instruments such as money market funds, SBN (Indonesian government bonds), deposits, or fixed income mutual funds based on your time horizon. Read how to reduce risk for the basic framework.

2. Across countries

Adding some global assets can reduce dependence on the Indonesian market. That does not mean moving 100% into the S&P 500. The articles why not just the IHSG? and why not just the S&P 500? explain the trade-offs.

3. Across time horizons

Money you need in 1 year and money for retirement in 20 years should not be treated the same way. Short-term money needs stability. Long-term money can handle more volatility.

4. Across income sources

People often forget this one. If your salary comes from the same sector as your stock portfolio, you can end up taking double risk. For example, if you work in commodities and your portfolio is also heavy in commodity stocks, a bad cycle can hit your job and your investments at the same time.

What should index fund investors do?

If you hold an Indonesian index fund, do a simple check.

Check the goal for this money

If this money is for a goal more than 10 years away, sector declines are part of the journey. Not pleasant, but not surprising.

If this money will be needed in 1-3 years, the real issue is not bank stocks or commodity stocks. The real issue is that short-term money is sitting in an asset that is too volatile.

Check your stock allocation

If a 10-20% drop keeps you awake at night, your stock allocation may simply be too high. The solution is not to guess sectors, but to lower portfolio risk through asset allocation and rebalancing.

Check whether you are too Indonesia-centric

Home bias is normal. We live in Indonesia, read Indonesian news, and naturally feel like we understand Indonesian stocks better. But a portfolio that is 100% Indonesia still carries country, currency, and sector risk.

Adding global assets gradually can make sense, especially for a portfolio that is already fairly large or for goals that include a foreign-currency component.

What you do not need to do

You do not need to sell everything just because banks are falling

Large banks are still important businesses in Indonesia. Their stock prices can fall because of profit expectations, valuation, foreign sentiment, or macro factors. That does not automatically mean the business is permanently damaged.

You do not need to buy commodity stocks just because they have already fallen

A stock that has fallen a lot can still fall much further. Commodities move in long cycles and are hard to predict. If you do not understand the business, do not treat a lower price as the only reason to buy.

You do not need to chase whichever sector is green right now

When one sector looks strong in a weak market, many investors feel tempted to switch. Often that move happens too late, after prices have already risen.

You do not need to abandon a passive strategy

A passive strategy never promises to outperform every single month. It relies on discipline, low costs, diversification, and time. If every sector drawdown makes you switch strategies, the benefit of being passive disappears.

Conclusion

Falling bank and commodity stocks are not just market headlines. They are a reminder that the IHSG has sector concentration and risks that are specific to Indonesia.

Passive investors do not need to become sudden sector analysts. What matters is making sure the portfolio is not fragile: the emergency fund is safe, the stock allocation matches your risk profile, short-term money is not sitting in stocks, and diversification does not stop at one country or one asset class.

The market will always have some sector that is hurting. Your portfolio should not end up permanently hurt because it depended too heavily on a single story.

Disclaimer: This article is for education only, not a recommendation to buy or sell stocks, mutual funds, or any specific sector. Always match your investments to your goals, time horizon, and personal risk profile.