Endowment Effect
Why do things we already own tend to feel more valuable than identical things we do not?
A position that has been held for a while begins to feel different from a new opportunity, even if the underlying characteristics are similar. Selling it can feel like giving something up, rather than simply making a decision. The attachment is subtle, but it influences how the position is viewed.
This is where the endowment effect begins to shape behaviour. Once something becomes part of what we own, it is often valued more highly than it would be if we were considering it for the first time. The difference is not based on objective value, but on the fact that ownership has changed the way it is perceived.
The effect was explored by Richard Thaler and later studied extensively by Daniel Kahneman, Jack Knetsch, and Richard Thaler. In simple experiments, participants were given an item, such as a mug, and then asked how much they would be willing to sell it for. Others, who did not own the item, were asked how much they would pay to acquire it. Consistently, sellers demanded significantly higher prices than buyers were willing to offer. Ownership alone changed the perceived value.
In markets, this can influence how positions are managed. Investments that are already held may be given the benefit of the doubt, even when alternatives offer similar or better opportunities. Selling can feel like a loss of something familiar, while holding feels like maintaining control. Over time, this can lead to portfolios that reflect past decisions more than current opportunities.
What makes this difficult to recognise is how natural it feels. Ownership creates familiarity, and familiarity often leads to comfort. The decision to hold does not feel like a bias. It feels like continuity.
You may notice this in yourself when you feel more attached to positions you already hold than to new ones, or when letting go of an investment feels more difficult than evaluating it objectively would suggest. There can also be a tendency to assign additional value simply because something is already yours.
The endowment effect doesn’t change what something is worth, but it does change how it feels to give it up.