Crisis bursátil: ？Es preferible una estrategia de gestión activa o pasiva?

index replication has become one of the most common current passive management strategies, supported by criticisms of active management in numerous academic works. however, no analysis has been made to determine if this technique is equally applicable during periods of stock market crisis compared to periods of bonanza in the market. in this work, a study is made of the relationship between trends in the spanish stock market and inefficiency in the medium plane variance of the ibex-35 index. the results indicate that inefficiency is reduced during periods when the market shows a tendency to rise, and proportionally to the increase in the profitability of the index. however, during periods of a falling market, the decrease in efficiency only occurs when the profitability of the index decreases. these results must be interpreted in accordance with the relative position of the index compared to the minimum global risk portfolio, under the hypothesis that the medium variance frontier and the index move in parallel fashion.