Over the period, there was a progressive increase in the total length of UK calls using national and international lines (NaIL) and mobile phones, while a curve was seen in the figures for local fixed-line (LFL) calls.
Should I use full capital letters (NAIL) or only capitalize the letters from the main words (NaIL)?
Also, if later in the essay, I want to write local fixed lines instead of local fixed-line, can I still use the abbreviation LFL?
(Note: Using initial letters only like this makes it so much easier for me to report data in the next paragraphs. However, I'm not sure if that makes my writing look sloppy. So, if it doesn't, ignore this note; if it does, please let me know)