Ninety-nine plans that improved will see a higher bonus payment applied to their benchmarks for 2014, according to Avalere.
High-performing plans also receive special markers on the plan-finder website, and other rewards from the Centers for Medicare and Medicaid Services.
Avalere also found the plans improved across several metrics, including patient experience and health outcomes.
The firm praised the upward trend in a statement.
"This is good news for Medicare beneficiaries," said Bonnie Washington, Avalere senior vice president, in statement.
"In 2013, beneficiaries will be able to choose from a greater number of high-quality plans that best meet their healthcare needs," she said.