One of the most fundamental elements of morale is the idea of a purpose larger than simply that of bringing home a paycheck, adding a sense of purpose or a particular goal to the motivations for an employee or a company in order to increase productivity. The fact is that when a reward (in most cases in the form of compensation) is attached to a task, intrinsic motivation generally decreases.
So if you can instill a sense of purpose in the workings of a company or in the mind of an employee, the intrinsic motivation to be productive or to do a good job with the tasks being given them increases, thus increasing productivity.
I think that you can find many studies that indicate how morale and productivity are strongly linked. On the most fundamental of levels, worker morale is extremely important to the productivity of workers. When individuals feel that they lack morale and lack a sense of voice in their workplace, they will not be as productive as if they would be if they felt a vested interest in the workplace. In the end, economic motives do underscore all business. Workers work for a paycheck. Owners work for profit. No one would suggest that morale trumps economic reality. Yet, I think you can find enough evidence out there to suggest that good things are usually close behind when management takes the interests of its workers into account. On a more theoretical level, the 21st Century workplace and the jobs in this setting are ones where individuals have to have a sense of freedom and space in constructing solutions to problems not even yet envisioned. This setting is one where worker morale is critical in that workers have to feel that they are valued enough to be trusted to solve problems. The workplace of this setting is not one where factorization and interchangeable parts dominates the scene as much as the construction of solutions which can only be done in a setting where individuals feel their voice, talents, and experiences are authenticated and valued. In short, a world where morale is highly evident.