Under fire for skyrocketing drug prices, pharmaceutical companies often offer this response: The high costs of their products are justified because the proceeds generate money for crucial research on new cures and treatments.

It’s a compelling argument, but only partly true. As a revealing new academic study shows, big pharmaceutical companies have spent more on share buybacks and dividends in a recent 10-year period than they did on research and development. The working paper, published on Thursday by the Institute for New Economic Thinking, is entitled “U.S. Pharma’s Financialized Business Model.”

The paper’s five authors concluded that from 2006 through 2015, the 18 drug companies in the Standard & Poor’s 500 index spent a combined $516 billion on buybacks and dividends. This exceeded by 11 percent the companies’ research and development spending of $465 billion during these years.

The authors contend that many big pharmaceutical companies are living off patents that are decades-old and have little to show in the way of new blockbuster drugs. But their share buybacks and dividend payments inoculate them against shareholders who might be concerned about lackluster research and development.