Depends no? If your "100%" is based on the after value rather than the before value, you have added 100%. Though I guess there is an implicit expectation that it is the before value that is used.
It went from having 0 pattern matching to having 1 pattern matching -- that seems like '100% more of this thing we are talking about' to me. This of course only makes sense if you see '1 pattern matching' as a precisely defined abstract construct, but I guess the 100%-more joke usually requires that perspective (and is a joke precisely because it's so non-sensical to think this way).
That really is a weird one, because here in the UK we say 'fortnightly' (for 'every other week'); so 'biweekly' would definitely be taken to mean 'twice per week'.
That also matches 'biannual' (an event that occurs every other year is 'biennial'), so 'biweekly' as 'fortnightly' is certainly to be proscribed, in my book.
I only have Collins' concise to hand, which gives the definitions I have and doesn't even mention (not even proscribed or US etc.) other uses. And Collins is pretty permissive.
And no they're not. 'Biennial' events occur once per two year period; 'biannual' events occur four times per two year (twice per year) period.
For example, in horticulture 'a biennial [plant]' is one that has a single flowering/reproduction cycle over two years. (Cf. 'annuals', 'perennials'.)
Except you do. If you go from 10 to 15, would have 50% more. The math: (15 - 10)/10. If you go from 0 to 1: (1-0)/0. Well, that is not gonna work, but it tends towards infinity as your starting number gets closer and closer to zero.
