You're right, I don't know. But what are the odds of my being infected? What's an acceptable risk? If I maintain social distancing and practice good hand washing and sanitizing, what are the odds of me infecting people? And for the record, I don't refuse to wear a mask. If a store's policy is that they require a mask, I wear one. It's a matter of simple respect. If they don't require a mask, chances are I won't wear one. Because in those stores, the workers aren't usually wearing masks, nor are most of the customers. But they do have the plastic partitions up, and the six foot markers. As long as I'm not sneezing, coughing, or talking to people, I just don't think the masks make that much difference.