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More than 40 percent of full-time private sector workers, the report said, lack access to either a pension or an employer-based retirement savings plan such as a 401(k).

Just under half—49 percent—say they participate in one.

While the study said that access can vary within a state, as well as from region to region across the country, it said that access varies more across the country’s metropolitan areas than across states as a whole. That said, it found that nearly three quarters of the U.S. metropolitan areas in the bottom 25 percent are in Florida, Texas, or California.

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It also identified specific regions and reasons for that lack of access, examining access in “metropolitan statistical areas” (MSAs), where it said approximately 51 million full-time, full-year private sector workers live—close to three quarters of all such workers in the U.S.

There’s wide variation in accessibility to an employer-based retirement plan, whether defined contribution or defined benefit. In Grand Rapids, Michigan, for instance, the study found that 71 percent of workers have access to a plan.

But in McAllen, Texas, the story is very different—only 23 percent of people can even choose whether to participate in an employer-based plan.

Here are five reasons access to retirement plans can be low in some U.S. metropolitan areas.

1. More people are working for small employers.

Pew said that previous analyses suggest that it’s harder for smaller businesses to offer retirement plans, since they face such obstacles as general financial uncertainties and the administrative costs of setting up and running plans.

Across the 50 states, the report found that only 22 percent of workers at companies with fewer than 10 employees report having access to a workplace retirement plan, compared with 74 percent of workers at businesses with at least 500 employees.

2. There are higher percentages of low-income workers.

Looking at the nation as a whole, workers who earn less than $25,000 in wages and salaries a year had an access rate more than 50 percentage points below the rate for workers earning $100,000 or more (22 percent vs. 75 percent).

If salaries are low, those lower-income workers will be less able to take advantage of a retirement plan even if it’s offered; they need their pay for everyday expenses.

3. There are higher percentages of Hispanic workers.

MSAs with high shares of Hispanic workers tend to have lower retirement plan coverage—such as the aforementioned McAllen, Texas, in which 95 percent of private sector workers are Hispanic.

The study said that Hispanic workers and other minorities may face barriers such as language or limited familiarity with financial institutions, factors that can limit both access and participation.

Nationally, the study found that just 38 percent of Hispanic workers reported having access to an employer-based retirement plan, compared with 63 percent of white, non-Hispanic workers.

Hispanic workers also have lower average incomes and are more likely to work in industries in which retirement plans are less common.

4. Retirement benefits are less common in some industries.

Some industries don’t generally offer retirement benefits, such as the leisure and hospitality sector or agriculture.

According to Pew’s review of national data, only 34 percent of workers in the leisure and hospitality industry had access to a retirement plan, compared with 69 percent of those working in manufacturing.

And since some industries tend to cluster in certain areas, that can result in a concentration of businesses that do not provide retirement benefits within a given MSA.

5. “Job quality” and other factors could determine retirement benefit availability.

Industries with large numbers of low-wage, short-term or part-time workers tend to have lower access rates.

Among other factors that play in to retirement plan access are the percentage of workers in certain industries, whether there is union representation, and the age composition of the workers.