It is now well established that multitasking is impacting productivity significantly. If you do a quick Google search with the terms “multitasking and productivity”, you will get over 1.4 million hits but the first few are quite interesting. The average reduction in productivity due to multitasking is estimated to be about 40%. Another interesting study related to impact on organization, across 45 different organizations, determined that the impact of reducing multitasking ranges from 13% to 150% increase in productivity.
In fact, what ever you do, including simple daily life tasks, multitasking simply means that each things you are doing simultaneously is done at less than full capacity, full attention.