Based on population per state, the number of new Covid-19 cases occurring in the past week is about the same in states with mask mandates and those without mask mandates.
A problem with this analysis is that it ignores the time dimension, as remarked on this blog, many times. States that did poorly in the past seem to do better in the present and states that did “everything right” in the past are now doing poorly. Because the virus spreads unequally in time – not all places have the same outcomes at the same time. The above analysis only looks at the past 7 days.
Their point is that face masks appear to have a minor affect and Biden’s claim that a national face mask mandate would change things is not supported by evidence.
Also, many states that do not have a state wide mask mandate, did, in fact, have local mask mandates in the major population centers. For example, Florida has no mask mandate but all of the major population centers have had them for months. Utah only just required face masks state wide, a week ago -but the counties around Salt Lake City, where almost everyone in the state lives, have had a mask mandate for a long time.
As I have remarked, we wear face masks in low risk environments like our mega hardware stores but do not wear face masks in high risk environments – like inside homes which appear to account for the majority of new cases.
The CDC has said that it is unable to quantify what part of reduction would come from face masks versus other measures, such as social distancing or sanitization. In other words, they don’t know. The CDC periodically publishes studies that “prove” face masks work – but do read the cited references. They rely on a few population studies that ignore the time dimension or they rely on simulations on models, not actual real world data.
To illustrate the time dimension problem, a studied published Sep 24 using data collected through August 15th, “proved” that face masks resulted in a 25% reduction in new cases in Ontario.
Of course, the study was out of date the day it was published as face masks immediately stopped working the day after they stopped collecting data, as seen by the steep rise, at right.
The quality of published work in public health appears to be utterly awful – this type of cherry picking, where the time dimension is missing is very common.