19.6 million people * 4 pills/person/day * 6 years ~= 172bn pills
Given that figure is significantly _more_ than the actual number prescribed, it doesn't strike me as overprescripton. Yes, there are issues with diversion, and the number of pain sufferers may be inflated by people faking pain (to get opioids or malingering for other reasons), but the volume of pills prescribed alone don't suggest there is a major issue.
Furthermore, 11.6 million 'true' high-impact chronic pain sufferers would still get you to the shipped figure, and I find it hard to believe that 8 million people are faking pain, especially as the data is gathered from a survey, rather than a situation that may result in opioids or any other non-clinical benefit.
 I (non-US) am on (up to) 8 opioid-containing pills per day, so taking 4 as a rough average doesn't seem unreasonable
 11.6 million people * 4 pills/person/day * 6 years ~= 101bn pills
For inflammation-type pain, paracetamol or NSAIDs (Nonsteroidal anti-inflammatory drugs) can be remarkably effective.
For neuropathic pain, gabapentoids are likely a better first-line treatment, with SNRIs (Serotonin–norepinephrine reuptake inhibitors) or TCAs (tricyclics) as second-line.
There are of course many people for whom opioids are appropriate, but they should only be used where less potentially harmful medications have been tried first. My understanding of the situation in the US is that they are often prescribed as 1st-line treatments, or inappropriately after surgeries where NSAIDs would be more appropriate.
I also wasn't attempting to do a rigorous accounting of all prescribed pills, but show that the 76bn figure _alone_ doesn't immediately point to overprescribing. It's a big number, but in context it doesn't seem out of the question. Furthermore, it doesn't rule out overprescribing, but that would require a more in-depth analysis than just looking that at the headline figure.
 "the dose is usually not more than 12 tablets per day" - https://www.mayoclinic.org/drugs-supplements/hydrocodone-and...
 "Roxicodone: Adults—10 to 30 milligrams (mg) every 4 hours as needed." https://www.mayoclinic.org/drugs-supplements/oxycodone-oral-...
 "At first, 15 to 60 milligrams (mg) every 4 hours as needed[...] the dose is usually not more than 360 mg per day." At the maximum daily dose, that puts you at 6 60mg pils/day, and in my non-US experience, the lower strength pills are often used to increase the dose of the combining drug (acetaminophen/paracetamol) - I am on 90mg/day, but it is still 8 pills https://www.mayoclinic.org/drugs-supplements/codeine-oral-ro...