Northsouth.
Think there is a pretty big trend towards larger aircraft and a bigger one towards more seats over the last 15 years or so .
Not difficult to see why ,the more you can pack in the more money you will make.
Recently both BA and LH to name just 2 are reducing legroom to get more in their short haul planes. Even though the slim line Recardo seats are claimed to give more pitch as base .
All about CASM.
Whilst the shorter haul planes are packing more in, the long haul are changing too, with many airlines squeezing another seat across to enable the 1st or business class to get more room up front.
There is also a newer trend towards premium economy.
Boeing are talking about scooping more out of the side walls of the planned 777-8/9X to make the increasingly( with airlines) popular 10 abreast more comfy.
Time will tell whether infact they can get enough to go an extra seat and whether Airbus will raise the floor of the A380 to go 11 abreast.
Think if airlines could get away with it they would try and shove 2 on each seat..lol...joking
Nigel