Does multitasking make someone more productive at work?

It is a commonly held belief that multitasking is a desirable attribute for an employee to possess. This is based on the idea that multitasking results in a higher volume of work product. However, the contrary view is that multitasking diminishes the quality of work. In other words, multitasking increases productivity if the goal is simply to produce more work product; but at the same time, it decreases the quality of each individual outcome.