Individual investors suffer significant losses from trading, with their aggregate portfolio experiencing an annual performance penalty of 3.8 percentage points. These losses amount to 2.2% of Taiwan's GDP or 2.8% of total personal income. Most of these losses are attributed to aggressive trading orders. In contrast, institutions benefit from trading, with an annual performance boost of 1.5 percentage points. Foreign institutions account for nearly half of institutional profits. The study uses comprehensive data from the Taiwan stock market to analyze trading behavior and its economic impact. Individual investors lose money due to aggressive trading, while institutions profit from both aggressive and passive trades. The study finds that trading losses for individuals are primarily due to aggressive orders, while institutional gains are partially offset by transaction costs. The results show that individual investors lose more than institutions gain, with losses attributed to trading, commissions, transaction taxes, and market timing. The study also highlights that institutional profits are largely due to passive trades, while aggressive trades benefit institutions. The findings suggest that individual investors are at a disadvantage in the market due to their trading behavior, while institutions benefit from their more strategic approach. The study provides evidence that individual trading leads to significant economic losses, while institutional trading leads to gains. The results have important implications for financial policy and investor behavior.Individual investors suffer significant losses from trading, with their aggregate portfolio experiencing an annual performance penalty of 3.8 percentage points. These losses amount to 2.2% of Taiwan's GDP or 2.8% of total personal income. Most of these losses are attributed to aggressive trading orders. In contrast, institutions benefit from trading, with an annual performance boost of 1.5 percentage points. Foreign institutions account for nearly half of institutional profits. The study uses comprehensive data from the Taiwan stock market to analyze trading behavior and its economic impact. Individual investors lose money due to aggressive trading, while institutions profit from both aggressive and passive trades. The study finds that trading losses for individuals are primarily due to aggressive orders, while institutional gains are partially offset by transaction costs. The results show that individual investors lose more than institutions gain, with losses attributed to trading, commissions, transaction taxes, and market timing. The study also highlights that institutional profits are largely due to passive trades, while aggressive trades benefit institutions. The findings suggest that individual investors are at a disadvantage in the market due to their trading behavior, while institutions benefit from their more strategic approach. The study provides evidence that individual trading leads to significant economic losses, while institutional trading leads to gains. The results have important implications for financial policy and investor behavior.