"Moreover, there were just 20 state settlements in 2014-2015, the lowest two-year total since 2006-2007. This reflected a dramatic decrease in federal financial penalties for unlawful drug promotion and a similarly sharp decline in the number of single-state settlements stemming from overcharging government health programs."

The report follows closely on the heels of news that the federal Centers for Medicare and Medicaid Services is about to launch a major initiative targeting insurance company overbillings for medical services. Public Citizen thinks state and federal regulators ought to be heading in that direction instead of retreating from enforcement.

And Public Citizen has a champion: U.S. presidential candidate Sen. Bernie Sanders, I-VT.

"Time and time again, drug companies defraud American taxpayers while making billions off government-granted monopolies," Sanders said in response to Public Citizen's report. "Enough is enough. The greed of the pharmaceutical industry must end. I urge my colleagues to stand up to the pharmaceutical industry and pass legislation to send a clear message that crime will no longer pay."

What's behind the drop in settlements and suits isn't clear, said Dr. Sammy Almashat, researcher with Public Citizen's Health Research Group and lead author of the report. Among the possibilities: a drop in federal enforcement, a shift in the focus of federal prosecutions away from off-label marketing and toward other forms of illegal activity, changes in state Medicaid pharmaceutical reimbursement strategies, and shifts in industry marketing strategies.

"We do know that, in addition to the rarity of executive accountability, previous penalties never have been large enough to deter the most common types of pharmaceutical fraud. So it would be surprising if the industry suddenly decided, of its own accord, to comply with laws it has routinely violated for decades," Almashat said.

Dr. Sidney Wolfe, founder and senior adviser to Public Citizen's Health Research Group, called for more scrutiny of Big Pharma and tougher penalties for wrongdoers.

"The recently reduced settlement activity is still indicative of ongoing, systematic wrongdoing, which is costing American consumers and taxpayers enormous sums and endangering patients. Larger financial penalties, especially for repeat offenders, and jail time for executives implicated in criminal activity might actually change the calculus, so that the consequences of lawbreaking are no longer just a cost of doing business for Big Pharma," he said.

Not surprisingly, the pharmaceutical industry believes the decline is a result of better behavior by drug makers. The lobbying group Pharmaceutical Research and Manufacturers of America said, "Biopharmaceutical companies are committed to legal and ethical conduct that serves the best interests of patients. The report makes scant mention of the tens of millions of dollars companies spend annually to develop and maintain state-of-the-art legal compliance programs."