プロスペクト理論: 利益と損失の確実性

Prospect theory explains how people evaluate potential gains and losses, often assigning greater weight to losses than equivalent gains.

Consider Sarah, an e-commerce business owner who is deciding between two marketing strategies.

The first guarantees a profit of $900 from a small campaign. The second offers a 90% chance of earning one thousand dollars but a 10% chance of earning nothing.

Despite the equal expected value, Sarah chooses the guaranteed $900, demonstrating risk aversion when dealing with gains. She values the certainty of profit over the potential for a slightly higher return.

However, Sarah's behavior changes when facing losses.

She must choose between accepting a guaranteed $900 loss on a failing product line or taking a 90% chance of losing $1000, with a 10% chance of losing nothing.

This time, Sarah opts for the gamble by taking a 90% chance of losing $1000, preferring the riskier option to avoid an inevitable loss.

This imbalance leads to risk-averse behavior for gains, where people choose the sure gain and risk-seeking behavior for losses, that is, taking the gamble over a sure loss in the hope of paying nothing.