Are happy workers productive worker

Yes, many studies carried out by psychologists and my own personal experiences working for different companies and different departments within companies, clearly show that happy workers are more productive. Happy workers have higher morale because of a more positive outlook that follows naturally from being happy.

The above is common sense; if you are happy working somewhere, wouldn't you want to stay and be more motivated do the job to the best of your ability, at the highest level of efficiency?