As always, it's hard to know if that exact number is precise. I've seen similar surveys citing percentages ranging from 40-80% (!) A lot may depend on how exactly the question is framed, and what a physician means when he or she says they are "considering" quitting.
But from numerous informal conversations with my colleagues, I can say there are significant numbers of physicians seeking an "exit strategy" from clinical medicine. Many more are hoping to just "hold on" until their kids get through college, etc.
Now there are some who argue this will be a non-issue, because there will always be plenty of young people eagerly applying to medical school. But I contend this analysis is mistaken.
There's already a projected shortage of doctors looming over the next 10 years, so any unanticipated early retirements will make things worse. This will translate into longer waits for patients.
Yes, new trainees entering the pipeline will partially make up for this shortfall. But we'll see a different kind of person choosing to enter medicine. There will be fewer of the fiercely independent types that I knew in medical school, and more of the types willing to submit quietly to bureaucratic decrees.
One contributing factor will be the "new medical ethics" being taught to many students, which explicitly states that a good doctor doesn't merely just advocate for his or her patient's best interests but should also balance the needs of "society". This gives them the moral fig leaf to help obey government edicts to deny care. They'll believe that restricting care is "the right thing to do".
Also, doctors employed by hospitals or managed by "Accountable Care Organizations" (as opposed to private practice) will be less incentivized to work hard, stay late, and put in that extra 5% of time/energy that can make the difference between nailing a difficult diagnosis vs. giving up and just following the cookbook treatment protocol.
In 10-15 years, there may be close to the same number of doctors "on the ground", but there will be a quality difference that might be hard for patients to discern but will be clear to doctors.