Multiple project assignment vs Productity

Unlike construction industry where basic implementation process is almost same for each building even though Architecture is different. In IT field, every Application or Project is different in design & implementation even though Architecture is same. Also, due to nature of work (in IT project/applications), one need to put concentrated effort till the design or development (unit work) is done to a logical level.
- Good amount of Time (sometime quality time) gets wasted in context switching and recollecting the things/point where you left on the other task other day.
- With multiple assignments comes multiple status meetings & reporting - another big overhead.
On an average you loose 10 to 15% of your time because of above twos.

- Priority (between tasks) is another major concern which results in conflicts and delays. Lesser priority work always suffers.

Either Schedule delay or Extra effort (by developers) is obvious and both effectiveness & productivity decreases overtime. There are many other hidden dimensions as well like higher Cost (due to extra coordination & delays), lesser quality (rush to complete the work), higher stress, strained relations etc..
So do we really gain by with this new mantra of multple assignment to acheive 100% utilization... my answer is Not Really !

In my view, any allocation below 50% is just mathematics (in MSP) where you can divide/multiply any numbers but certainly not logical for development work to complete any meaningful task (not talking about trivial taks).
Assignments (tasks) should always be logically related and should Never be more than two.