Employment data are showing improvements in some ways. Unemployment is now down to its lowest level in six years and the economy has created almost 2.2 million jobs in the past 12 months. Unfortunately, many of those jobs are part time and more than 7.5 million part-time workers would prefer to hold full-time positions.

Recessions always create conditions where millions of workers are forced to accept part-time work. Recoveries usually create opportunities for full-time employment.

In June, 5.4 percent of the workforce reported being employed part time for economic reasons. Most were unable to find full-time work because of "slack work or business conditions," according to the Bureau of Labor Statistics.

Before the recession, 3.3 percent of workers wanted full-time work, but were forced to take part-time jobs. That percentage was below 4 percent from 1994 until 2008.

There are no signs the situation will change for the better in the near term.

June data showed that 20.2 percent of jobs were part time, up from 19.7 percent in May. Before the recession less than 18 percent of jobs were part time.

There are a number of financial incentives for employers to use part-time workers instead of full-time workers. Many of these incentives were created by government mandates. Part-time workers earn less than full-time workers do, and the large pool of part-timers will hold down wage growth. Consumers will struggle to meet rising expenses of necessities and discretionary spending will decline, leading to an extended period of slow economic growth.

In this environment, it seems investors will also struggle and face below-average returns until economic growth recovers.