Here’s a quote from today’s Globe and Mail :
I often see these patterns in The Economist, too.
A. Why don’t they write “from 10 per cent to 25 per cent”, like a normal person would?
B. Why the hyphen between 200 and billion? I don’t think anybody would write “I have 50-dollars in my wallet”.
Have I misunderstood English all this time? Or is it a style guide thing?
In the second case, I’d strongly suspect that it’s a matter of their style guide; i might suspect that they feel that adding the hyphen ensures that the reader clearly understands that the “US$200” is connected to the word “billion”.
That’s actually a little ambiguous - it could mean “increasing tariffs to a range within 10 and 25 percent, depending on the goods involved”
Billion used to mean million million in Britain - maybe this is left over from that.
As for the other, the newsworthy thing is the 25%, so I understand why they would put it first.
You mean the kind of ambiguity that would be lifted if they just wrote “200 billion US$” ? 
As a “classically” educated retired journalist, I will add yeah, what everyone else said.
This is almost universally the answer to any question of why a traditional journalist writes anything the way they do. The style guide exists to ensure that things I write look like the things you write when they get to print. And if the decisions made by the style guide come across as weird, you can usually be assured there was someone in their development who hated the way they used to do it where they used to work and was determined to not do it that way here.
NPR used to (based upon what I heard on air) require any reference to an event occurring in the past use the largest time division appropriate to the distance in the past when referring to the event. Consequently, if you heard a news report that made reference to, say, a trial verdict that happened last week, they would say “the verdict which came out last week,” unless, say, yesterday was the first of the month, in which case they would say “the verdict which came out last month.” I never actually heard them describe something that happened “yesterday” as having happened “last year,” but it would have been entirely consistent.
I doubt if style guides are used as much as you suggest. The number of glaring spelling, grammar and other errors I see both online and in print journalism today indicates that proofreading is a lost art. Or at least an ignored one. Many errors show that computer-based spelling assists are also not used. If text is proofread so little, I doubt if styles are any more important.
If you mean their use of decade and century, I’m totally with you. You often hear things like “The family owned bakery has been operating for nearly a quarter century” or “The home was vacant for over three decades.” Just give us the number. Both local and national content does this.
I can’t say I recognize the yesterday/last month thing.
I agree. Where style guides are important – in magazines like the New Yorker, for example – proofreading is also rigorous and general respect for language is part of the culture. In most mass media it’s gone to hell. To make matters worse, many science and technology articles are written by scientifically illiterate imbeciles, so you get bad writing not only filled with grammatical and typographical errors, but factual errors, too.
“Used to”? It’s changed?
Yes. Britain mostly changed over to the short scale where “billion” means a thousand million in 1974 to conform to international usage.
It has been changed for a while, so to remember it you’d have to (a) have been listening for a long time and (b) have been pissed off by it enough to still hold something of a grudge over it.
I, for one, have been bitching about it here on the Dope since at least 2002.