I am looking for articles or reports, preferably freely accessible,
that comment on the effects of politics, law, business practice,
economic and demographic trends, technology etc on the quantitative
and qualitative demand for middle-level and senior managers in
business organisations in developed countries generally and the UK in
particular. My purpose is to explore these influences and their
consequences over the next five years.

A great answer will provide links to up to ten relevant materials and
will favour sources that support their conclusions with data rather
than solely speculation.