I apologize. My first post was unclear. That's my fault. I don't need any more evidence to convince me that wearing a mask will help to block some of the droplets. I wish they were better, but they do something and I wear one without protest at all times when I'm inside a public building.
What I was getting at, which I tried to clarify in my second post, is research into when it really is necessary to wear a mask outdoors. I liked zzzz's answer and have read most of the same things, but I haven't seen the actual research to back it up.
When I am outside, I usually do not wear a mask, but that is because I am not in a large group. I always have a mask with me in case I can't maintain distance. I went running for about 50 minutes today in a local regional park. I probably had the mask on 10 times, but never for more than about 15 seconds. In two instances, the trail was wide, but I had to go by large groups (9 people and 12 people if I counted correctly). No masks in one group and about half masked in the other, but there was no way to keep distance. There was no internal debate in either situation. Mask on as I ran through. In another instance, I passed a family of three. Looked like a mom, a dad, and a kid who was probably about 10. All had masks. Mom and Dad did their best to move far to the side. The kid was oblivious. Either way though, that section of trail was much more narrow. We could have all been as far to the sides of the trail as possible and there would have been less than three feet of separation. So again, mask on. No internal debate. The other times were all times where the trail was wide but for whatever reason, it was going to be close. In those situations, I ended up putting the mask on basically because of what we don't know yet and because I'd rather have it on and have those others be comfortable than to ruin their experience in the park. At the same time, in each of those cases, I really felt like my risk was minimal even without a mask on.
But again, those behaviors are formed by my opinions and biases. I know what I want the answer to be, which is why I put the mask on in those circumstances anyway. Because I recognize that I haven't really arrived at those opinions due to good science. I've arrived at them based on what I hope that science will eventually find. Maybe it will and maybe it won't, but right now, there isn't that much science to go on at least that I have seen.