1. button
2. gotten
3. mountain
4. eaten
5. wait
In all of these examples the t is dropped entirely in all but the most formal speech. Unless you mean something different this is not a new phenomenon and is actually a characteristic marker of American English. In fact everyone I know, even people 30-40 years older than me, drop their t's everywhere. It actually feels weird to me to pronounce them in the above example and it sounds like I am scolding someone. I don't really know the linguistic history of it and my family has only been here a few generations, but everyone back to my grandparents spoke this way. Perhaps it wasn't as common before the 30's though.
As for news and what-not I'm so used to it I didn't even notice any change in inflection. NPR tends to be very hip these days (unfortunately) and so I am not surprised they are speaking more casually than a normal newcaster.
See https://en.wikipedia.org/wiki/Flapping and https://en.wikipedia.org/wiki/T-glottalization
Time-consuming for sure. But not even remotely difficult in terms of rigor or replicability. And if you're familiar with the International Phonetic Alphabet, you'll see that pronunciation is something that can be analyzed extremely objectively.
The claim is explicitly non-categorical, as the usage of the word "tend" shows.
>It seems hard to measure, quantize and produce rigorous and replicable results.
Not really.
First you split your informers into groups, based on sex, social class and/or education level. Then you pick a linguistic variation that you know to be stigmatised, but still present in that group regardless. Then you analyse the frequency that that feature appears, in comparison with another variation for the same feature.
If I recall correctly one of the first to notice those gender discrepancies in speech was Labov, so you might have some luck if you websearch "gender paradox Labov".
The hypothesis was that upper class women pronounced the "r" as in "Fourth", but lower class women "rolled the r" so "Fourth" became "fowth".
The researchers entered department stores with high and low end customers and asked for a product that was "on the Fourth floor", then they counted the number of times the "r" was pronounced or "rolled"
I can still talk in a reasonably posh way, but almost never use it, and adopt all sorts of mannerisms from my travels, my accent is, at a guess, a little bit estuary english, with other things thrown in.
I've never really felt the need to up my accent, it doesn't make you the most popular person professionally to act better than everyone else, especially if you don't have vastly superior skills or superior standing to back it up, in fact it annoys me if someone tries it on me. I wouldn't say I act lower class than my standing, rather, I tend to fit in with my peers.
I think I only heard in it in some African American English accents when I first came here, but now it’s common among younger Americans more generally. I’ve also heard it applied to other consonants - you can replace quite a few of them with a glottal stop and still be understood :D
Haven't noticed it yet (New Yorker), but will surely keep my distance from/cringe at such silly people.
Note: not fluent yet, please if you speak German correct me if my depiction is not accurate. “Bavarian German” does seem to drop a lot of the condiment sounds, and also seems to drift closer to Latin in some ways, but I haven’t had time to actually look into that.