Prescription drug prices have been rising at a blistering rate over the last few decades. Between 1980 and 2016, overall spending on prescription drugs rose from about $12 billion to roughly $330 billion, while its share of total health care spending doubled, from 5% to 10%.

Although lawmakers have shown renewed interest in addressing the problem, with pharmaceutical CEOs testifying before the Senate Finance Committee in February and pharmacy benefit managers (PBMS) scheduled to do so this week, no comprehensive plan to halt the relentless increase in prices has been proposed, let alone agreed upon.

Robin Feldman, a professor at the University of California Hastings College of Law, takes a look at the drug pricing system in a new book, “Drugs, Money and Secret Handshakes: The Unstoppable Growth of Prescription Drug Prices.” In a recent conversation with Bloomberg’s Joe Nocera, Feldman said that one of the key drivers of rising prices is the ongoing effort of pharmaceutical companies to maintain control of the market.

Fearing competition from lower-cost generics, drugmakers began over the last 10 or 15 years to focus on innovations “outside of the lab,” Feldman said. These innovations include paying PBMs to reduce competition from generics; creating complex systems of rebates to PBMs, hospitals and doctors to maintain high prices; and gaming the patent system to extend monopoly pricing power.

Feldman’s research on the dynamics of the drug market led her to formulate three general solutions for the problem of ever-rising prices:

1) Transparency: The current system thrives on secret deals between drug companies and middlemen. Transparency “lets competitors figure out how to compete and it lets regulators see where the bad behaviors occur,” Feldman says.

2) Patent limitations: Drugmakers have become experts at extending patents on existing drugs, often by making minor modifications in formulation, dosage or delivery. Feldman says that 78% of drugs getting new patents are actually old drugs gaining another round of protection, and thus another round of production and pricing exclusivity. A “one-and-done” patent system would eliminate this increasingly common strategy.

3) Simplification: Feldman says that “complexity breeds opportunity,” and warns that the U.S. “drug price system is so complex that the gaming opportunities are endless.” While “ruthless simplification” of regulatory rules and approval systems could help eliminate some of those opportunities, Feldman says that the U.S. doesn’t seem to be moving in this direction.

Read the full interview at Bloomberg News.