Have you ever wondered just how important a role the 401(k) plays in the retirement plans of American workers?

Well, we now have an answer: the starring (and sometimes solo) role.

According to Fidelity Investments, 55 percent of 1,000 recently surveyed Americans say they would not be saving for retirement if they did not have a 401(k), and 19 percent say their 401(k) is their only savings for retirement.

The survey also shows that 33 percent of workers are in an employer-sponsored pension plan, 28 percent have savings in bank accounts and 28 percent have investments in stocks or bonds. Pre-retirees 55 and older are the most active users of IRAs, with 44 percent saying they utilize these retirement-savings investments.