Developed countries tend to have around 25% of their GDP in manufacturing but only 20% of their employees in manufacturing.
The number of employees per unit of manufacturing has been dropping for years.
One take:
http://www.bloomberg.com/news/articles/2014-04-28/why-factory-jobs-are-shrinking-everywhere
By “developed countries”, is this the UN’s term, which replaced First and Second World? Remember, they still define Red China (formerly “Second World”) as “developing”.