a 1.9 would just be under 800,000 homes, rule of thumb is every 1.0 = 400,000 homes.
PPV event back in 1988 were few but the channels were there to provide the event.
TV has evolved from just 4 channels to 5 then the cable era started and dish network etc, 1988 they (guessing for example) had 5 main stations and 30 cable channels now they have 5 main stations with there version of freeview ie 100 channels and cable/dish with over 400 channels. That why the ratings decades ago were better because the was not much choice now theres a channel for almost everything.
a 1.9 in 1997 was still a big number for the amount of channels to view
extra added
Mike Tyson vs Evander Holyfield (rematch), June 1997 - 1.99 million PPV buy (wcw did well with a 1.9)