By definition, companies know more about the abilities of their own workers than they do about those of outsiders. But they still opt for the latter, even though research suggests that outside hires take three years longer to perform as well as internal candidates in the same job. They also pay outsiders more.
— Read on www.economist.com/business/2019/05/05/why-companies-are-so-bad-at-hiring
I’ve seen this up close.