The number of employees calling in sick to work with fake excuses is holding steady at one-third among U.S. workers each year but fewer are getting fired for it, according to research released on Tuesday.

Most employers typically do not question absences, but 15 percent said they fired an employee for missing work without a legitimate excuse this year, said the survey conducted for CareerBuilder.com, an online jobs site.

Last year, more employers, 18 percent, fired employees absent without legitimate excuses, the research showed.

The number of U.S. employers who check up on absent workers declined to 29 percent this year from 31 percent last year and 35 percent the year before, the research showed.

This year, 28 percent of employers said they think more employees are absent with fake excuses due to stress and burnout caused by the recession, the survey said. The researchers did not ask a similar question in earlier surveys.

"Especially in this economy, employers respect the fact that a lot of employees are burned out and probably more likely to understand their excuses, regardless of what they are," said Allison Nawoj, spokeswoman for CareerBuilder.com.

The number of workers calling in sick when they are not at least once a year has held steady at one-third in 2009, 2008 and 2007, the survey said.

Also holding steady has been the two-thirds of employers who say they let workers use sick days as so-called mental health days, the research showed.

Of employers who check on absent employees, most required a doctor's note. Others called the employee at home, had another worker call or drove by the employee's home, it said.

Among the reasons for falsely calling in sick, the most frequently cited was not feeling like going to work, followed by doctor's appointments, a need to relax, catching up on sleep, errands, avoiding a work-related event, housework and spending time with family and friends. Childcare was not listed as an option in the survey.

The online survey was conducted by Harris Interactive on behalf of CareerBuilder.com among 3,163 U.S. hiring managers and human resource professionals and 4,721 U.S. full-time adult workers between August 20 and September 9.

The margin of error among the workers was plus or minus 1.74 percentage points. Among the hiring managers and human resource professionals, the margin of error was plus or minus 1.43 percentage points.

CareerBuilder is owned by Gannett Co, Tribune Company, The McClatchy Co and Microsoft Corp Corp.