Several states are taking steps to create retirement savings plans for private-sector workers whose employers don’t offer retirement plans, trying to overcome what one state legislator calls “a crisis of unpreparedness for retirement.”

Illinois state Sen. Daniel Biss was one of the speakers Tuesday on a panel discussing new developments in defined contribution plans at Pensions & Investments’ Global Future of Retirement conference in New York.

“The big issue is a lack of access to employer-sponsored plans,” Mr. Biss said. “This population is not saving enough for retirement.”

People without access to employer-sponsored retirement plans are “a forgotten category” in all states, said Mr. Biss, who was the author of a bill that was signed into law in January creating the Illinois Secure Choice Savings Program, to help private-sector workers whose employers don’t offer a retirement plan.

In Connecticut, a 2013 study found that 40% of employed residents between the ages of 25 and 64 didn’t have access to an employer-sponsored retirement plan, said Kevin Lembo, state comptroller.

Mr. Lembo is co-chairman, with state Treasurer Denise Nappier, of the Connecticut Retirement Security Board, which was created last year to study and develop a statewide plan open to private-sector workers who aren’t covered by employer-sponsored plans.

Employers, especially those with few workers, “must be engaged in the design and implementation processes to ensure their support and reduce any burdens placed on them by the program,” Mr. Lembo said.

Although some states are looking for ways to help private-sector employees, many others are taking steps to change their public defined benefit plans. Many of these changes in state retirement systems primarily have affected new public employees, said Joshua Franzel, vice president of research for the Center for State and Local Government Excellence, a non-partisan research organization.

Citing several research sources measuring changes since 2008, Mr. Franzel noted that increased vesting periods, reduced benefits, increased eligibility requirements and changes in plan design have had a greater impact on new employees than existing employees.

Only in the case of increased contribution rates has the impact been greater on existing employees, Mr. Franzel said. Reductions in pension funds’ cost-of-living allowances have affected new and existing employees about the same, but retirees have been hit hardest by this policy, he added.