reading 18经典题 approaches to portfolio construction 中第3题，看到security-specific factors时，老师说这是bottom up。这跟这部分经典题第1题，讲解fund 2时说，“it targets individual securities that reflect the manager’s view that growth firms will outperform value firms”，看到factor，可以是top down也可以是bottom up是否矛盾
