To get your mind around the concept of productivity, imagine a small, insular farming village in which all of the good land is being farmed and every household grows or makes whatever it uses -- from food to the house itself. Further suppose that a stranger walks into town looking for work.
If you subscribe to the "lump of labor" theory, then this guy is out of luck. The only way he could go to work would be by farming part of someone else's land. If he eats more, someone else must eat less.
But that's not how the world works. Suppose the guy who walks into town has figured out how to build a more effective plow. He can sell his plows to farmers, who will pay for them with a share of their more bountiful harvests. Not only will our stranger have a job, but the farmers will be growing and eating more -- even after paying for their new plows.
We can do it again: A second stranger walks into town and offers to set up a school -- or make clothes, or build houses, or design irrigation ditches, or do anything that frees up the farmers to spend more time cultivating their crops. Again, crop yields go up. And again, we've created another job.
Productivity is an important aspect of growth. Population growth and other factors are not as important as productivity, which is usually a better estimate for economic growth.
Currently, Italy is making reforms to its public sector in an attempt to curtail some of its reputation for poor public service and increase productivity. There was an agreement between Luigi Nicolais, the minister in charge of public reform, with the trade union federations – CGIL (Confederazione Italiana Generale del Lavoro), CISL (Confederazione Italiana Sindacati Lavoratori) and UIL (Unione Italiana del Lavoro) – which represented state employees at negotiations.
So as Wheelen tells us about increasing productivity, an investment in education, innovation, specialization, and sensible tax and regulatory policies are what are necessary to maximizing productivity. The public sector reform is just one small part of one of these elements.