In theory, this is a "medical trial" and any trial has a certain percentage of the population that is given a placebo. I tried to find something about how the percentage is computed but it gets a little complicated.

I did find this one piece and what caught my eye was this on clinical trials:

Since 2000, the total number of registered clinical studies worldwide has risen. There were only 2119 registered clinical trials globally back in 2000. Come 2015 it was 205,372. In 2016, there were 233,171 registered. And, there were 262,361 in 2017, 293,341 in 2018, and 318,091 registered as of October 2019.

https://comparecamp.com/placebo-effect-statistics/