What is seat width on UA 787 in Y?

There has been a lot of talk about reduced seat width in the 787 to squeeze in extra seats, but I can't find any data on the actual seat width.

On UA.COM, they define "Seat Width" but the term doesn't exist elsewhere on the page:

http://www.united.com/web/en-US/cont...0/default.aspx

On Seatexpert.com, they say it's "unknown"

http://seatexpert.com/seatmap/691/Un...oeing_787-800/

And, it's simply not mentioned on SeatGuru.com.

When I do a Google search, I find a ton of articles that talk about how much narrower the seats are but found none that provide measurements.

In contrast, Seatexpert reports a width of 17" on the 747:

http://seatexpert.com/seatmap/319/Un...nternational)/

And, they report 18" on the 777.

And, UA reports the same:

http://www.united.com/web/en-US/cont...7/default.aspx

http://www.united.com/web/en-US/cont...0/default.aspx

Is there any data on seat width on the 787? Why is it so hard to find?