Why Bayesian Investors Keep Beating Everyone Else
July 11, 2026
One of the biggest mistakes investors make is believing that markets reward certainty. They do not. Markets reward investors who assign better probabilities than everyone else and, more importantly, who are willing to update those probabilities as new evidence emerges. That distinction may appear subtle, but it changes almost every investment decision because investing has never been about predicting the future with absolute confidence. It has always been an exercise in weighing incomplete information, assigning rational odds to competing outcomes, and having the discipline to adjust those odds when the facts change rather than when emotions demand they should.
Most investors approach the market by asking a deceptively simple question: What do I think will happen? A Bayesian investor approaches the same situation from an entirely different direction by asking, Given everything I know today, what is the most probable outcome, and how should that probability change as new information becomes available? The difference is profound because it replaces certainty with adaptability. Instead of becoming emotionally attached to a forecast, the investor becomes attached to the process of continuously improving it.
Indonesia’s current MSCI review provides an excellent example of why this distinction matters.
Much of the commentary surrounding the review has become polarised into two opposing camps. One side argues that a downgrade is virtually inevitable because governance concerns remain unresolved, while the other dismisses those concerns entirely by pointing to Indonesia’s strong economic growth and long-term structural story. Both perspectives suffer from the same weakness. They mistake conviction for probability and, in doing so, ignore the fact that financial markets rarely operate in absolutes.
The most important development occurred in June when MSCI had every opportunity to move directly towards a downgrade but instead chose to extend its consultation period. That decision should not be dismissed as administrative housekeeping because it immediately alters the probability distribution. Had MSCI concluded that Indonesia’s accessibility issues were effectively irreversible, or believed there was no meaningful political commitment to reform, extending the review would have served little purpose. Instead, the organisation effectively signalled that concerns remain, but that further evidence is warranted before reaching a final conclusion. That is not a guarantee of success, nor should it be interpreted as one, but it does reduce the probability of an immediate negative outcome.
This is precisely how Bayesian thinking works. New evidence does not produce certainty. It produces an updated estimate.
The positive evidence is substantial and should not be ignored. Indonesia continues to grow at roughly five percent annually despite a difficult global environment, inflation remains relatively well contained, the banking system has demonstrated resilience, and large-scale investment continues flowing into downstream nickel, copper, batteries, smelting, manufacturing, energy and digital infrastructure. Perhaps even more important is the government’s incentive structure. Developing deeper and more trusted capital markets lowers the country’s cost of capital, attracts long-term institutional investment, improves IPO activity, strengthens pension participation and ultimately supports national economic development. Whether those reforms are motivated by idealism or economic self-interest matters very little if the implementation proves successful.
At the same time, the negative evidence remains entirely legitimate. Free-float concerns have not disappeared, corporate governance still requires improvement, foreign institutional confidence has yet to fully recover, and implementation risk remains significant because announcing reforms is considerably easier than demonstrating they function consistently over time. Four months is also a relatively short period in which to convince global institutional investors that structural market changes are both genuine and durable.
The critical observation is that these two groups of evidence address entirely different questions. The positive evidence largely concerns Indonesia’s economic trajectory and long-term productive capacity, while the negative evidence concerns the accessibility and governance of its capital markets. Those subjects are related, but they are not interchangeable. MSCI is not attempting to forecast Indonesia’s GDP growth in 2035, nor is it evaluating the quality of the country’s natural resources or demographic profile. Its mandate is considerably narrower. It wants to know whether international institutional investors can deploy and withdraw capital efficiently, whether free-float requirements accurately reflect market reality, whether ownership structures are sufficiently transparent, and whether disclosure standards allow global funds to replicate benchmark indices without undue distortion.
Recognising that distinction prevents Bayesian analysis from degenerating into blind optimism. Strong economic fundamentals improve the environment in which reforms can succeed, but they do not automatically satisfy the operational standards MSCI is evaluating. The economy influences the probabilities without determining the outcome.
Based on the evidence available today, my own probability distribution would place roughly a 55 to 60 percent chance on MSCI closing the review favourably, or at least removing the negative bias while retaining Indonesia’s current classification. I would assign approximately a 20 to 25 percent probability that Indonesia retains its status while MSCI continues monitoring implementation for a longer period, leaving perhaps a 15 to 20 percent probability that the review ultimately results in a downgrade. Those figures are not predictions of what will happen. They are simply the most rational estimates that can be formed using the evidence currently available, and they should continue evolving as additional information emerges over the coming months.
This is also where the market may be creating an opportunity.
Suppose investors are currently behaving as though downgrade risk sits somewhere between forty and fifty percent, while the evidence suggests the probability is materially lower. That difference represents far more than an academic exercise. It represents the foundation of every successful contrarian investment because markets do not require certainty to rerate assets. They simply require the probability of an adverse outcome to decline. As uncertainty fades, investors demand a smaller risk premium, valuations begin expanding, and prices adjust accordingly, often well before complete certainty ever arrives.
The sequence is easy to imagine. In June, MSCI expresses serious concerns and the market reacts by aggressively discounting the possibility of a negative outcome. By September, reforms begin showing measurable progress and investors gradually reduce the probability of a downgrade. By November, MSCI either closes the review positively or acknowledges sufficient progress while continuing to monitor implementation, leading investors to reduce the required risk premium once again. Nothing fundamental has changed overnight. What has changed is the market’s assessment of the probabilities, and markets have always repriced probabilities long before they reprice certainties.
This principle extends well beyond Indonesia because it describes the essence of intelligent investing. Every successful contrarian investment begins with the same observation: the market is assigning one set of probabilities while the available evidence supports another. Sometimes investors underestimate risk and become excessively optimistic. At other times they become anchored to recent disappointments and assign far greater probabilities to negative outcomes than the evidence actually justifies. The objective is never to prove the crowd completely wrong. It is to identify situations where the crowd’s probability distribution has become materially disconnected from reality.
That is precisely why attempting to identify exact market tops and bottoms has always struck us as an exercise in frustration. Markets can remain irrational for extended periods, and nobody consistently identifies turning points with precision. Probabilities, however, evolve continuously as earnings reports, policy decisions, regulatory announcements, capital expenditure plans and macroeconomic data gradually reshape the balance of evidence. Investors willing to update their views rationally gain an advantage that compounds quietly over time because they are responding to reality rather than defending yesterday’s opinions.
The best investors rarely succeed because they possess superior certainty. They succeed because they possess superior adaptability, recognising that every new piece of evidence deserves to be incorporated into their thinking without becoming emotionally attached to conclusions formed months earlier. Over decades, that discipline compounds into something remarkably powerful because markets rarely reward those who are most confident. They reward those who consistently assign better probabilities than the crowd and have the intellectual humility to change their minds when the evidence demands it.
