PMI has recently brought clear answers to this question on the following page.
It explains why the changes were necessary, essentially due to the evolution of the Project Management profession, and how the exam itself is impacted: Newly added content and different weight allocated to the domains covered by the exam

You’ll get answers to these key questions:
- Why is the PMP exam changing?
- What’s been updated and why?
- How do these changes impact the PMP exam content?
- What is the difference between an RDS update and a PMBOK® Guide update ?
