As tens of thousands of Americans die from prescription opioid overdoses each year, an exclusive analysis by CNN and researchers at Harvard University found that opioid manufacturers are paying physicians huge sums of money - and the more opioids a doctor prescribes, the more money he or she makes. The CNN/Harvard analysis looked at 2014 and 2015, during which time more than 811,000 doctors wrote prescriptions to Medicare patients. Of those, nearly half wrote at least one prescription for opioids. Fifty-four percent of those doctors - more than 200,000 physicians - received a payment from pharmaceutical companies that make opioids. Among doctors in the top 25th percentile of opioid prescribers by volume, 72% received payments. Among those in the top fifth percentile, 84% received payments. Among the very biggest prescribers ... 95% received payments. On average, doctors whose opioid prescription volume ranked among the top 5% nationally received twice as much money from the opioid manufacturers, compared with doctors whose prescription volume was in the median. Pharmaceutical company payments to doctors are not unique to opioids. Drug companies pay doctors billions of dollars for various services. In 2015, 48% of physicians received some pharmaceutical payment. The CNN and Harvard findings are in line with other studies suggesting that money from drug companies does influence a doctor's prescribing habits.