Mary is absolutely correct. Up until 1990, Kingdom Halls were built to serve a community once the existing KH was getting too crowded. As cities and towns expanded and grew, new Kingdom Halls were built to serve the suburbs and growing nearby cities. But it seemed that the best size for a KH was a population of 80-130 total publishers and their family members.
In the late 1950s, as dedicated publishers left their home congregations "to go where the need was greater," KHs were built with smaller populations in mind. The goal was to put a Kingdom Hall in as many towns as possible so that non-JWs would be more inclined to come to public talks and the Memorial meeting.
Now Kingdom Halls are being built as little assembly halls, some actually having two or more congregations meeting with simultaneous or overlapping times. Some areas have multiple congregations meeting in the same KH, but on different week nights and staggered Sunday meetings. I understand that a few even have the traditional Sunday meetings on Saturdays.
One interesting development is the introduction of Sunday morning meetings. Growing up, Sunday AMs were field service hours, as were Saturday AMs. I really doubt that they have moved service hours to Sunday afternoons after the WT study in those areas.
One last development: Many KHs won their zoning variances based on past history of one evening meeting per week and a 2-3 hour meeting on Sunday afternoons or evenings. Now they are merging Kingdom Halls, so that there are meetings almost every night, plus ALL DAY Sundays and some Saturdays. I'm sure the neighbors did not expect all that additional traffic and street parking in their quiet residential areas.
Way to go, WT! Piss off the neighbors, why don't you?
JV