Yep, there's a reasonable chance this analysis suffers survivorship bias. Outliers whose stock-prices severally crashed are less likely to be represented. Hence

Yep, there's a reasonable chance this analysis suffers survivorship bias. Outliers whose stock-prices severally crashed are less likely to be represented. Hence, impactful sell recommendations are probably missing from the data, explaining why sell-side recommendations don't appear to to perform as well.