Not within the past four weeks, but I’ve been on vacation. It’s possible I would have sent one had I been in the office. It’s not something I have to do too often, but I sometimes have to submit a signed document for something like my medical flexible spending account and faxing is much faster than the US mail and slightly faster than scanning the document, emailing it to myself (don’t have a scanner attached to my work computer), and then emailing it to the right place.
I just sent and received faxes yesterday. It doesn’t happen too often, most of the agents prefer to email documents, but sometimes we get an agent who either doesn’t like email or doesn’t have access to a scanner.
The fax I sent was actually to another department in the same building. Why I couldn’t just walk the printout to the other department is beyond me. I keep expecting to find a “Department of Redundancy Department” somewhere in the building.
Not in the past four weeks, no. But I did send a fax to the US in May.
Part of the idea of picking a specific window of time (the past 4 weeks, in this case) is that presumably the people who almost never send or receive a fax, but have done so in the past 4 weeks, and the people who frequently do so, but for some reason haven’t in the past 4 weeks, balance out to give a true picture of the degree of fax use.
At least, true for a self-selected subsample of a somewhat esoteric subpopulation, but not much I can do here about those limitations. 
I sent one for a customer sometime in the last year, but not within four weeks.
Received: definitely yes. Many companies who buy from the company I work for still send purchase orders by fax. We have a paperless system that turns the faxes into image files and sends them to an email account.
Sent: probably not. I send everything by email unless I absolutely have no email address for them. It’s just so much faster. Faxing is a pain in the ass.
I knew some jobs still used them, but I’m surprised by how well the faxers are doing. And, no, it’s not more secure than email. Emails can be encrypted. Faxes can’t.