The declining trend in the proportion of women having annual mammograms can be attributed to questions over the clinical efficacy of the exams, the out-of-pocket costs--which is even more hard felt in today's tough economy---and a shortage of radiologists and technicians.

In February, a Centers for Disease Control and Prevention (CDC) study noted a slight decline in the proportion of women having annual mammograms in almost every state in the nation.

While the drop is so small that researchers call it a "declining tendency," it echoes similar findings in recent years. A National Institutes of Health study published in 2007 found that while the percentage of women 40 and older having yearly mammograms grew steadily between 1987 and 2000, those rates leveled off for three years and then declined, reported the Washington Post.

Additionally, an earlier five-year telephone analysis conducted by the CDC found that the percentage of respondents who had gotten a mammogram in the preceding two years dropped from 76.4 percent in 2000 to 74.6 percent in 2005--numbers which translate to 1.1 million fewer women getting routinely screened nationwide, according to the Post.

Recommendations on how often a woman should get screened vary slightly. The U.S Preventive Services Task Force, an independent panel of experts working under the Department of Health and Human Services, recommends that women older than 40 get a mammogram every one to two years. Other groups, such as the American Medical Association, suggest that the test should be done every year.

However, experts have reported seeing gaps beyond two years. Many women understand the need to have a mammogram but don't go back for repeat tests after the first one, according to Carol Lee, chair of the American College of Radiology's (ACR) Breast Imaging Commission and a radiologist at the Memorial Sloan-Kettering Cancer Center in New York City.

One factor that experts attribute the slight decline to is the uncertaintly about whether a positive mammogram, particularly for women in their 40s, is more likely to save a woman's life by having treatment started promptly or to expose her to lengthy, harsh treatments that might not have been necessary, reported the Post.

Also, since it is not currently possible to be sure which very small breast cancers found by screening will cause problems and which breast cancers will not, most of the medical community continues to rely on mammograms as a detective tool.

"Doubt over effectiveness is far from the only reason many women are not getting mammograms, and many might well choose to get the test if they could overcome other barriers," said Susan Brown, a nurse and head of health education for the Susan G. Komen Foundation, a breast cancer advocacy group. These reasons include cost, fear of pain and inconvenience.

Many people are forgoing preventive tests due to lost jobs and associated health insurance, according to Mark Rukavina, executive director of the Access Project, a health reform advocacy group. The Post reported that the out-of-pocket cost for a mammogram ranges from about $135 to $270. And although insurance co-pays for mammograms tend to range from $10 to $35 or a bit higher, Rukavina said that "even that small fee could seem insurmountable stacked against other costs right now."

Cost may be less an onerous issue than many expect, since some insurers do not charge a mammogram co-pay as part of some of their plans. Also, organizations like the Komen Foundation and community health centers can sometimes direct women to mammography centers that offer screenings free or on a sliding fee scale, based on income, reported the Post.

Lastly, while finding a place to have a mammogram is a problem in parts of the country, because of a shortage of radiologists and technicians, many are reporting seeing an increase in the number of radiology students interested in reading mammograms, according to Lee.