This screen image shows the Web site for Maryland's online health care exchange. (AP Photo/State of Maryland) (AP/AP)

The overwhelming majority of Maryland residents who used the state’s troubled online marketplace to sign up for health insurance made possible by the Affordable Care Act have become customers of CareFirst, a massive and well-known insurance provider based in Maryland.

State health officials say that of the 72,207 Marylanders who signed up for a plan through the marketplace during the first enrollment period, 67,800 picked a CareFirst plan — which was often the least expensive offering. That’s 94 percent of enrollments.

The Kaiser Foundation Health Plan received 3,560 new customers. Evergreen Health, a new cooperative that hoped to get thousands of customers via the exchange, had 525 sign-ups through the site. United Healthcare had 322.

All of those customers signed up during the first open enrollment period, from Oct. 1 to March 31. The state’s Web site did not function as expected during that period, which made it much more difficult for many Marylanders to enroll.

The state is in the process of replacing its Web site before the next open enrollment period starts Nov. 15.

One of the flaws with the first site: For months, plans were listed based on premium price, putting lower-priced CareFirst plans at the top and forcing shoppers to extensively search if they wanted other options. Peter Beilenson, founder and president of Evergreen, has said that this flaw, along with the general dysfunction of Maryland’s site, unfairly hurt his start-up and forced it to quickly change its business plan, targeting businesses instead of individuals. Beilenson hopes that once the state replaces its Web site with technology that has worked in Connecticut, consumers will be able to fully vet all of their choices, factoring in perks and costs beyond the monthly premium.

For the next open enrollment period, CareFirst has proposed increasing its premiums by 23 to 30 percent, a hefty increase that the Maryland Insurance Administration has yet to approve. Kaiser has proposed decreasing its rates by 12 percent, while Evergreen has proposed a decrease of 10 percent.

Some other statistics recently released by Maryland health officials:

• Of those who enrolled in private plans through the marketplace, 54 percent were women.

• Montgomery County had 20,430 enrollments, the most in the state. (See a map of county-by-county results.)

• Seventy percent of enrollees were older than 35 years old, and more than half were older than 45.

Here’s the breakdown provided by the exchange: Younger than 18, 2,199 sign-ups (3 percent); ages 18 to 25, 6,249 (8.7 percent); ages 26 to 34, 13,178 (18.3 percent); ages 35 to 44, 3,370 (18.5 percent); ages 45 to 54, 17,011 (23.6 percent); ages 55 to 64, 18,253 (25.3 percent); 65 and older, 1,947 (2.7 percent).

• More than 70 percent of Marylanders opted for plans that cover more expenses.

The exchange ranks its plans on a metallic scale, with bronze plans having the most out-of-pocket expenses and platinum plans offering the fewest.

About 28 percent of shoppers opted for bronze plans, while 53.6 percent went for silver plans, 12 percent picked gold plans and 5.5 percent signed up for platinum. The exchange also offered “catastrophic” plans with limited flexibility, but only 429 people — less than 1 percent of shoppers — picked that option.