When jotting down quick notes for my own reference, I use one line- but this is because my handwriting is small and rather closed (loops/curves/circles) and if I try for two lines it just becomes unreadable.
When I am making an effort to write nicely for either another person’s reference or something that will be on display to be read, I use two lines- because that’s what I think of as more “correct”.
Although I do both, I voted for “two lines” in the poll because that’s what I think of as proper whereas the single line is something I use for expediency and readability when only for my own reference.
Incidentally, not that it’s authoritative or anything, but a Google Image search for “dollar sign” yields the “two lines” version for 4 of the first 10 results.
Ha ha. In my mind there are two, but I only write one. Apparently I do just give up at the last step and go, “That final strike is too far.” I just leafed through some notes I scribbled, and the second line does not appear anywhere.
A lot of older typewriters use the two-line dollar sign. That was where I learned what they should look like, so that’s what I usually write.
For a long time I believed that the symbol was just the superposition of U and S (with the bottom of the U cut off), so I assumed that this was just the natural and correct way to write it. In recent years I’ve learned that this history of the $ symbol is generally considered hor$e$hit.
I found out that in US you should put two because it’s a S with a U in it with the bottom part of the U cut off. See? It’s now US! Either way works though. I use two and it never looks sloppy either… One is too little though! It looks like not enough to me.
When I’m just writing down a dollar amount, I tend to use one line. When I’m spelling words with dollar signs to be cool, I’ll often use two lines. Ke$ha’s album covers (here and here) both have two lines in the dollar sign, so that’s why I’ve started using the two lines more often.