Obamacare will see a drop in signups by as much as 13 percent during this year's open enrollment, S&P Global Ratings predicts.

Nov. 1 to Dec. 15 marks the fifth year of open enrollment, and the forecasts by S&P show that 10.6 million to 11.4 million people will sign up for Obamacare plans, meaning signups could fall by as little as 7 percent. Last year, 12.2 million customers signed up, though the Department of Health and Human Services had set its targets at 13.8 million. Former Obama administration officials said that the shortfall was attributable to the Trump administration pulling TV ads during the last 10 days of open enrollment, when President Trump entered the Oval Office, noting that enrollment was on track up to that point.

The Department of Health and Human Services is not setting a target for enrollment this year.

"Our target this year is to have a seamless open enrollment for consumers," Randy Pate, deputy administrator for the Centers for Medicare and Medicaid Services, said in a phone interview with the Washington Examiner. "That's what we are focused on. The numbers we think will take care of themselves."

The S&P projections take into account several factors, including that open enrollment is shorter this year, that the federal government won't be advertising Obamacare as much and that the cost of premiums will rise for people who don't receive subsidies. Under Obamacare, about 8.7 million people do not receive subsidies under Obamacare and many buy coverage outside of the exchanges, according to the Kaiser Family Foundation.

Premiums are rising because of a variety of factors, including that Trump ended payments to insurers known as cost-sharing reduction subsidies. To make up for the difference, insurers have raised the prices of premiums. About 80 percent of Obamacare customers who buy coverage on the exchanges are shielded from the increases because the federal government kicks in additional assistance to keep their premium expenses consistent.

According to another analysis released Monday by the left-leaning Center for American Progress, enrollment without those factors would be projected to reach the same level as last year's open enrollment, at 12.2 million, of which 8.1 million would be customers enrolled this year and 4.1 million would be new customers. The group has accused the Trump administration of trying to "sabotage" Obamacare.

The S&P predictions show that fewer new customers will enroll through the exchanges but that those likely to continue buying the plans are customers who paid their premiums during the full year in 2017. The number of people who pay their premiums all year is smaller than the number of people who sign up during open enrollment. For instance, during the first three years of open enrollment about a quarter of people who signed up didn't pay for the full year of premiums. Some people drop out, while others get jobs that offer coverage or have a life change such as a marriage or divorce that changes the kind of health coverage they get.

The report's analysts suggested that enrollment in Obamacare may have plateaued because of the portion of people who don't pay for their plans all year and because certain parts of the population are still not convinced they must buy the coverage offered under the law.

"We don't expect [enrollment] to grow meaningfully above 9 million without active outreach to the eligible individuals who remain uninsured," S&P analysts wrote. "Insurance remains a product that is sold rather than bought, and this is especially the case when trying to gain wider acceptance for health insurance among individuals who consider themselves young and invincible."

Insurers have often said that selling Obamacare plans has been difficult to those who are young and healthy. Without those customers, insurers raise costs as those who buy plans file more expensive medical claims, which subsequently results in higher-priced premiums in later years.