Conviction Can Kill Your Returns. Aswath Damodaran Explains Why

Key Concepts

• Concentration vs. Diversification: The debate regarding focusing investments in a few holdings versus spreading them across many.
• Conviction (in investing): The speaker’s skepticism towards relying heavily on the concept of “conviction” in stock selection.
• Portfolio Turnover: The rate at which investments are bought and sold within a portfolio.
• Mature vs. Younger Companies: The differing risk profiles and diversification needs based on the types of companies invested in.
• Portfolio Size (Number of Stocks): The optimal number of stocks to hold for risk management and potential returns.

The Concentration vs. Diversification Debate

The central topic addressed is the ongoing debate among investors regarding portfolio construction: whether to concentrate investments in a small number of stocks or to diversify across a larger number. The speaker firmly advocates for diversification, expressing skepticism towards the popular notion that strong “conviction” justifies concentration. He explicitly states he lacks the confidence, even after extensive research, to limit his holdings to as few as five stocks, believing the risk is too high.

The Speaker’s Diversification Strategy

The speaker’s personal approach involves holding between 30 and 45 stocks at any given time. This number isn’t arbitrary; it’s influenced by his investment style, which includes a significant allocation to younger, potentially higher-growth, but also higher-risk companies. He acknowledges that investors focusing solely on mature, established companies might be able to adequately diversify with a portfolio of 15 to 20 stocks.

He emphasizes the long-term nature of his holdings, noting a low portfolio turnover rate of only three or four stocks sold and replaced annually. This indicates a buy-and-hold strategy focused on identifying quality companies rather than frequent trading.

Perspective on "Conviction" and Risk Management

The speaker directly challenges the overuse of the term “conviction” in investment discussions. He doesn’t elaborate on why he finds it overused, but the context suggests he believes it can lead to overconfidence and insufficient risk mitigation. His diversification strategy is explicitly framed as a risk management technique. He aims to avoid a scenario where a single company’s negative performance significantly impacts his overall portfolio.

As he states, “I don't want any individual company in my portfolio to have a day where I look at my portfolio and say, 'Oh my god, what happened here?'” This highlights a preference for minimizing potential downside risk.

Scale and Proportion of Diversification

To contextualize the number of stocks held (30-45), the speaker points out the sheer number of publicly traded companies – over 45,000. He argues that holding 40 stocks represents being “incredibly picky” rather than excessively diversified, given the vast investment universe. This framing shifts the perspective from a large absolute number to a small percentage of available options.

Logical Connections & Synthesis

The argument progresses logically from the initial debate (concentration vs. diversification) to the speaker’s personal strategy, the rationale behind that strategy (risk management and investment style), and a contextualization of the portfolio size. The core takeaway is that diversification, particularly when investing in a mix of younger and mature companies, is a prudent approach to managing risk and avoiding catastrophic losses. The speaker’s low turnover rate further reinforces the idea of a long-term, thoughtful investment process rather than speculative trading.