Next year will mark the 10th anniversary of ProPublica’s Dollars for Docs, our ambitious effort to track pharmaceutical company payments to doctors.

When we started, we were thrilled to gain access to what seven drug companies paid physicians for speaking and consulting and to collect payment information in a first-of-its-kind database that allowed everyone to search for their doctors in one place. Now, federal law requires every drug and medical device maker, about 1,700 companies, to release information on their payments.

In the years since its launch, Dollars for Docs has become an essential tool for patients and has been viewed more than 23 million times. But from the very start we were bedeviled by a simple question: Were the drug company payments linked to doctors’ drug choices?

The answer, it turns out, is a resounding yes, as my colleague Hannah Fresques reported today. But making that connection was a long and complex process that relied heavily on the relentless — and creative — pursuit of data by tag teams of ProPublica reporters.

From the start, we knew that having the drug company payments wasn’t enough. We also needed to gain access to what drugs doctors prescribed, information that is traditionally private. Some doctors who received payments, we reasoned, probably prescribed just like their peers. And some probably didn’t.

In 2013, Tracy Weber, Jennifer LaFleur and I convinced Medicare to give us data on the prescriptions written in its massive Part D prescription drug program, more than one of every four prescriptions written nationwide. It was a big step toward our goal. We analyzed the data on the drugs doctors prescribed and created a lookup tool, called Prescriber Checkup, that allowed people to compare their doctors to peers in the same specialty and state.

Our analysis gave us the first signs that the drug company payments were linked to prescribing: Some of the top prescribers of expensive, brand-name drugs had financial relationships with the drugs’ makers. This included the beta blocker Bystolic, taken for high blood pressure, and H.P. Acthar Gel, which is approved to treat a variety of ailments.

Matching the Medicare data with payment data was more difficult than we imagined because doctors were identified one way in one database and another way in the other.

In 2016, we had a breakthrough. Working with my ProPublica colleagues Ryann Grochowski Jones and Mike Tigas, we were able to link physician identification numbers in the Medicare prescribing data with those in a federal database of pharma company payments to doctors.

For the first time, we could map a widespread pattern: Doctors who received payments from the pharmaceutical industry prescribed drugs differently than their colleagues who didn’t. And the more money those doctors received, on average, the more brand-name medications they prescribed.

But this analysis didn’t look at specific drugs, it looked at payments overall and the share of a doctor’s prescribing that was for brand-name drugs.

Since then, we’ve worked to look at the connections between drug company money and a doctor’s prescribing habits in a more granular way. For Fresques’ new analysis, she examined the top 50 brand-name drugs prescribed to patients in Medicare Part D for which drug companies made payments to doctors. She found that for 46 of the 50 drugs prescribed in 2016, doctors who received payments related to a specific drug that year wrote more prescriptions for the drug than doctors who didn’t.

In 2016, for example, doctors who received payments related to Myrbetriq, which treats overactive bladder, wrote 64% more prescriptions for the drug than those who did not. For Restasis, used to treat chronic dry eye, doctors who received payments wrote 141% more prescriptions.

“If there are physicians out there that deny that there is a relationship, they are starting to look more and more like climate deniers in the face of the growing evidence,” Aaron Kesselheim, a professor of medicine at Harvard Medical School and an expert in pharmaceutical costs and regulation, told Fresques.

Fresques’ analysis did not look at whether the pharma payments caused doctors to prescribe more of a drug. And indeed, both companies and doctors defend their work together, saying they are providing information so that physicians can make better choices for patients.

Today, we’re not just releasing our analysis, we’re taking steps to make the information useful for consumers. We are updating our Prescriber Checkup tool to let users see whether their doctors received a payment related to any of the top 50 brand-name drugs in Medicare that they also prescribed.

We recognize that doctors have many reasons for prescribing a drug, but now consumers will have the information to ask if compensation or financial relationships are among them.