Warren Buffett's 7 Investment Principles: How to Choose Good Stocks and the Keys to Long-Term Investing
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Warren Buffett's investment philosophy centers on understanding businesses, evaluating their competitive advantages and management, buying at reasonable prices relative to intrinsic value, and holding investments for the long term. Managing downside risk and minimizing investment costs are also essential. However, the '7 principles' are not a single official list established by Buffett, but a summary of seven core ideas found in Berkshire Hathaway's shareholder letters.
These principles remain useful for investors as of 2026-10-11, but that does not mean investing in individual stocks is suitable for everyone.
Buffett has suggested low-cost index funds as an alternative for ordinary investors who find it difficult to analyze individual companies.
1. Invest Only in Businesses You Understand
The first criterion Warren Buffett emphasizes is whether an investor can understand a company's business model and how it generates revenue.
In Berkshire Hathaway's 1996 shareholder letter, Buffett explained that investors do not need to be experts in every industry. What matters is recognizing the boundaries of what they can competently evaluate.
This is commonly called the 'Circle of Competence.'
For example, suppose a company's stock price is rising rapidly.
If you cannot explain what products the company sells, why customers buy them, or how its profitability might change when competitors enter the market, it will be difficult to assess its value.
Conversely, familiarity with an industry does not automatically make a company a good investment. Understanding a business and determining a fair price for its stock are separate matters.
Individual investors can ask themselves the following questions before buying:
Where does the company generate most of its revenue?
Why do customers choose this company over its competitors?
What risks could reduce the company's earnings?
If these questions are difficult to answer, you may not yet have enough information to make an informed investment decision.
2. Look for Companies with Durable Competitive Advantages
When Buffett evaluates a company, he considers not only its current earnings but also whether it can maintain its competitive advantages in the future.
A representative concept is the 'Economic Moat.' Just as a moat protects a castle, an economic moat refers to business strengths that help a company maintain profitability despite competition.
Economic moats can take many forms.
Some companies have strong brand loyalty that encourages repeat purchases, while others benefit from low production costs that allow them to offer more competitive prices.
Berkshire Hathaway's 2013 shareholder letter described the low operating costs of auto insurer GEICO as an example of a competitive advantage.
However, owning a famous brand does not guarantee that a company's competitive advantages will last forever.
To evaluate a company's competitive position, investors should examine not only market share but also profitability, customer retention, cost structure, and the competitive environment.
3. Even a Great Company Can Be a Bad Investment at Too High a Price
Warren Buffett's approach to value investing is different from simply buying stocks whose prices have fallen significantly.
The key is distinguishing a company's intrinsic value from the price at which its shares trade in the market.
Intrinsic value is an estimate of the present value of the economic benefits a company is expected to generate in the future. The stock price is the actual price at which its shares trade in the market.
These two values may differ.
For example, suppose a company's intrinsic value is estimated at KRW 100,000 per share, while its market price is KRW 80,000. The shares would then be trading at a price KRW 20,000 below their estimated value.
According to the author's calculation, the discount is:
(KRW 100,000 - KRW 80,000) ÷ KRW 100,000 × 100 = 20%
However, this 20% is not a guaranteed investment return.
That is because the intrinsic value of KRW 100,000 is itself an estimate based on assumptions about future earnings, discount rates, and other factors. If the company's growth falls short of expectations, its intrinsic value may also decline.
Value investors must therefore examine not only why a stock appears inexpensive but also the possibility that their own estimate of the company's value is incorrect.
4. View Stocks as Ownership in Businesses, Not Just Price Quotes
Buffett views stock investing as acquiring partial ownership of a business.
Berkshire Hathaway's 2024 shareholder letter also reflects the perspective that publicly traded stocks should be evaluated as partial ownership interests in businesses.
From this perspective, a company's actual ability to generate profits becomes more important than daily movements in its stock price.
For example, suppose a company's share price falls 15% over one month.
That fact alone does not establish that the company's value has declined by exactly 15%.
Investors need to examine whether revenue and earnings have deteriorated, competitive advantages have weakened, or debt burdens have increased.
Conversely, even if the share price has not fallen, a deterioration in the company's ability to generate earnings may justify reassessing the investment.
A Decline in Stock Price Is Not the Same as a Deterioration in Business Value.
However, investors should not automatically interpret a falling share price as an opportunity to buy more. The market's assessment of the company's future cash flows may have changed.
5. Invest for the Long Term, but Keep Reviewing Your Reasons for Holding
Buffett's approach to long-term investing is not simply about holding stocks for a long time.
In his 1996 shareholder letter, Buffett described an investment perspective that considers how a company's earnings might change over the next 5 years, 10 years, and 20 years.
If an investor buys shares without assessing the company's long-term earnings potential, simply extending the holding period will not necessarily improve the investment decision.
The effect of compounding helps illustrate the significance of long-term investing.
Suppose an initial investment of KRW 10,000,000 grows by 7% each year. The results would be as follows.
| Investment Period | Amount Assuming 7% Annual Growth |
|---|---|
| Initial investment | KRW 10,000,000 |
| 10 years | Approximately KRW 19,670,000 |
| 20 years | Approximately KRW 38,700,000 |
| 30 years | Approximately KRW 76,120,000 |
This is a simplified compound-growth example calculated using `KRW 10,000,000 × (1.07)^number of investment years`. It does not account for taxes, fees, or inflation, nor does it imply that actual stock returns remain constant every year.
For long-term holding to be meaningful, a company must continue creating value.
Buffett himself acknowledged in Berkshire Hathaway's 2024 shareholder letter that he had made mistakes in assessing the future economics of businesses and evaluating management.
Long-term investing therefore requires not only patience but also periodic reviews of whether the original investment thesis remains valid.
6. Consider Potential Losses First and Reduce Unnecessary Risks
Risk management is as important to Warren Buffett's investment philosophy as pursuing high returns.
However, the principle of avoiding losses should not be interpreted to mean that an investment must never experience an unrealized loss.
Stocks are assets whose prices fluctuate according to corporate performance and market conditions. Even high-quality companies can produce investment losses depending on when their shares are purchased and at what price.
Investors should be particularly cautious about expecting large short-term gains without adequately understanding a business or buying shares solely because their prices are rising.
In his 2013 shareholder letter, Buffett discussed the danger of investors being influenced by overheated market sentiment and investing solely on expectations of further price increases.
The practical implications for individual investors are relatively straightforward.
They should separate living expenses and money needed in the near future from investment capital, while considering how the failure of a particular investment could affect their overall assets.
Even investors who are confident in their analysis of a company cannot predict the future with complete accuracy.
Risk management is less about developing a technique that prevents all losses and more about preparing so that an incorrect judgment does not lead to consequences that are too difficult to bear.
7. Manage Investment Costs and Behavior Rather Than Trying to Predict the Market
Warren Buffett has emphasized that ordinary investors may be better served by focusing on diversification and low costs rather than attempting to predict short-term market movements.
In his 1996 shareholder letter, he explained that low-cost index funds could be a useful option for most investors.
In his 2013 shareholder letter, he emphasized that individual investors can diversify across multiple companies even if they cannot accurately predict the future earnings of each business.
In particular, Buffett described the following asset allocation instructions in connection with the management of his estate at that time:
90%: An S&P500 index fund with extremely low management costs
10%: Short-term U.S. Treasury securities
Buffett proposed this allocation for a specific estate-management purpose. It is not a universal asset allocation formula that every individual investor should follow.
An appropriate portfolio depends on an investor's age, income, investment horizon, risk tolerance, and country of residence.
Korean investors considering U.S. equity ETFs should evaluate not only a fund's management fees but also exchange-rate fluctuations, tax treatment, and tracking error.
Diversification can also help reduce risks concentrated in individual companies, but it cannot eliminate the risk of a decline across the entire stock market.
How to Apply Warren Buffett's Investment Principles When Analyzing Stocks
The seven principles are easier to understand when connected into a single investment decision-making process rather than applied separately.
First, determine whether you understand the business. Next, evaluate its competitive advantages and financial condition. Then compare the company's value with its market price and decide whether there is a sound reason to hold the investment for the long term.
| Evaluation Stage | What Investors Should Examine |
|---|---|
| Business understanding | Revenue structure and major customers |
| Competitive advantage | Cost advantages and competitive environment |
| Financial health | Debt, earnings, and cash flow |
| Business valuation | Expected earnings and current stock price |
| Holding decision | Long-term earnings potential |
| Risk management | Portfolio allocation and acceptable loss levels |
| Investment approach | Direct stock investing or low-cost diversified investing |
For example, if you discover a company with growing revenue, you can examine whether its operating profit and cash flow are also increasing before immediately buying its shares.
Even when revenue rises, profits may decline if costs grow faster.
It is also important to distinguish between concluding that a company is good and concluding that its current share price is reasonable. Even a company with strong long-term growth prospects may deliver disappointing returns if its shares are purchased at an excessively high price.
If valuing individual companies is difficult, investors can also consider spreading their investments across multiple businesses through vehicles such as index funds.
Is Warren Buffett's Investment Approach Suitable for Beginners?
Warren Buffett's investment philosophy offers valuable lessons for beginners, but that does not necessarily mean copying his approach to selecting individual stocks is the best strategy.
Buffett has emphasized the importance of understanding business models and evaluating future earnings. At the same time, he has recommended low-cost index funds for ordinary investors who find it difficult to devote sufficient time to such analysis.
There is an important distinction here.
Investing in individual stocks requires judgments about specific companies, while investing in a broad market index allows investors to spread their investments across many businesses.
Of course, index funds can also result in a loss of principal, and their risks vary depending on the market and index they track.
Therefore, investors with limited experience may be better served by first defining their investment horizon and risk tolerance rather than trying to predict which stocks will rise.
Warren Buffett's seven principles can be brought together into the following investment approach.
Find Businesses You Understand, Evaluate Their Competitive Strengths and Value, and Pursue Long-Term Returns at Reasonable Prices and Within Acceptable Risk Levels.
And if you lack the time or ability to evaluate individual businesses, choosing not to force yourself into stock picking is also consistent with Buffett's investment philosophy.
Knowing the limits of your own judgment is just as important as being able to identify good businesses.
※ This article is provided for informational purposes to help readers understand market dynamics and does not constitute a recommendation to invest in any particular stock or asset. Investors are responsible for their own final decisions and investment outcomes.
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