In surveying freelancers, independent contractors, and on-demand or temporary workers (rather than people who make money through rentals, such as Airbnb or selling goods via such services as Etsy), the study found that of the three segments of workers it identified, gig-only workers not only come off considerably worse than traditional workers regarding current pay, but their potential for retirement is also threatened.

The three types of workers identified by the survey are gig-only, gig-plus (those who do gig work but also have either a full-time or part-time job) and full-time (those with traditional full-time jobs). Gig-only workers live with "less stability of income and 'job security,' have to self-fund their benefits and retirement savings and pay self-employment taxes," the report points out, but here's the kicker.

Gig-only workers on average make just $36,500 annually, compared to full-time employees who make an average of $62,700 per year. They do work fewer hours—a median of 25, compared to full-timers' 40 hours—but gig-plus workers also make less than full-timers, averaging $55,800, despite working an average of 44 hours compared to full-timers' 40. That makes it tough for them to keep up with day-to-day financial needs.

And then there are all those extras toward which employers contribute for full-time workers—the insurance premiums, taxes and retirement savings that full-timers benefit from and gig workers don't. With gig workers having to meet those additional financial obligations, they have a tougher time trying to achieve financial goals. They don't have access to employer-sponsored retirement plans, meaning that even if they do manage to save for retirement they miss out on employer contributions. Only 16% of gig-only workers have assets in an employer-sponsored retirement plan, compared with 56% of full-timers.

And even gig-plus workers are missing out, with just 25% of them having assets in an employer-sponsored plan—and those retirement assets, the study adds, could be due to their traditional non-gig work, or to a spouse, a plan sponsored by a previous employer, or an affiliation with a professional association.

While this lack of access to benefits isn't good for any level of gig worker, 54% of gig-only workers have no access to employer-based benefits, such as health insurance (40% compared with 82% of full-timers), life insurance (20% compared with 59%), dental insurance (25% compared with 66%) and short-term disability (5% compared with 42%)—younger gig workers (ages 18–35) are less likely to have access to benefits (70%) than the 44% of gig workers over age 55 who have access.

And gig-only workers, the study finds, are working because they need to, not because they want to. Close to half, 44%, say that gig work is "nothing more than helping to pay the bills," and nearly a third say they needed a way to bring in income due to circumstances out of their control. They're also more likely to be older, at an average age of 47 compared with 43 for full-time workers); single, divorced, separated, or widowed (51% compared with 36%); and either retired, a stay-at-home parent or student (35% compared with 9% of full-timers).

And they're likely not to be happy about their circumstances. Gig-only workers are less satisfied with their current work situation than full-time employees (44%, compared with 55%), and they're less likely to feel financially secure or stable, with just 50% of gig-only workers saying so compared with 59% of full-timers.

Gig-only workers most commonly cite the lack of benefits as the top disadvantage of gig work, followed by the lack of consistency of earnings and predictability of demand for work. But even full-timers who expressed interest in switching to gig work (32%) cite lack of benefits as a deterrent, and also say that indicate that the gig model would have to evolve to generate consistent pay and benefits to incentivize them to switch.