A question asked elsewhere was how many letters did you write in 2018? I didn't actually count but I reckon over 300 letters. I did however keep a record of when letters/postcards came in, and when I posted mail too so I could tot the numbers up. I did not mind the question though.
I did used to give monthly stats but stopped because it may not be fair to say, "Look at me, look how many letters I write, look how much money I have spent on postage stamps, look how many penpals I have got!" Besides, perhaps I do not want to admit/realise how much money I spend on postage (or even how much stationery I bought last year - at least most of it was in the sales)! One of my penpals has over 150 other penfriends. Some might say that she is a penpal collector, and how can her letters be unique? Her letters are unique, and the ones to me are written just for me.
I could say how many different people I have written to in the past year, but I won't do that. With the likes of Facebook and the possibility of showing others how many "friends" you have on there, and Twitter & Instagram with followers, penpalling is not a popularity contest. It doesn't matter how many penpals you or I have. For me, it is the quality of the letter, the connection that I find is more important than quantity / popularity. For personal reference, though, it may be informative.
What I might do when February has started & finished for 2019, is to count up the number of surprise letters received and sent through InCoWriMo-2019.