You could probably work it out to get an idea using available stats.
The New York City went into lock down on the: 22nd of March, 2020 ( Hypothetically masks are mandatory)
add 14 days for incubation period, the pre-mask infection peak would have occurred by 5th of April 2020.
Any cases after that would reflect the wearing of masks.
It is now 5 days after the pre-mask infection peak.
Austria:
Austria is to join a small but growing number of European countries making the wearing of face masks outside the home compulsory amid shifting debate over the medical gear’s protective utility. Authorities would start distributing millions of free face masks at the entrances to all supermarkets from midweek onwards, chancellor Sebastian Kurz announced on Monday. Shoppers will only be permitted inside supermarkets and other open stores, such as pharmacies, if they are wearing masks. While masks are a familiar sight throughout Asia, the only other countries in Europe to require the wearing of masks in public space are Slovakia, the Czech Republic and Bosnia-Herzegovina.
Czech Republic:
According to official sources in the Czech republic the spread of the virus can be reduced by 80% by simply using a face covering like a mask, towel etc..
Wearing a simple cloth mask, decreases the spread of the virus by 80 %! Czech Republic has made it OBLIGATORY for its citizens to wear a mask in the public.
https://www.theguardian.com/world/2...ing-masks-after-government-decree-coronavirus
You do understand that it is not about
you maintaining separation only but about others doing the same?
It is about others spitting on you as they speak or breath or cough etc...
and you spitting on them as you speak, cough , sneeze or other ....
"I protect you as you protect me" sort of thing...ie...
Also shutting the gate ( Putting on a mask) after the horse has bolted is not going to be much help is it?
So in a pandemic, when is the best time to start using a mask?
After people start dropping dead around you or before? ( rhetorical)