For the reasons you describe, it seems to me futile to assess the efficacy of masks from observational data. Has anyone looked at the actual mechanism, the filtering out of particles of certain sizes, studying the size range of virus-carrying particles, the different mask materials, and so on? That seems a lot more useful than ever-higher piles of statistics. I remember seeing studies about that about a year ago, but nothing recently.
For the reasons you describe, it seems to me futile to assess the efficacy of masks from observational data. Has anyone looked at the actual mechanism, the filtering out of particles of certain sizes, studying the size range of virus-carrying particles, the different mask materials, and so on? That seems a lot more useful than ever-higher piles of statistics. I remember seeing studies about that about a year ago, but nothing recently.