I think WTC is doing everything they can to make KHs a reliable revenue stream - but it is still not enough. More are fading and the only "new" ones coming in are born-ins. Eventually they leave also.
My experience as Acct Servant was that the bulk of the contributions came from 10-15% of the members. Typically older retired publishers (mostly women) who had a nice retirement and who had accumulated a nice nest egg. I recall one elderly sister who every month would write a $100 check for each contribution box. Local. WWW. KH Building. . . . and any special fund that was added, ie, bringing missionaries home for conventions. She was a little ditzy and I suspect her non-witness family members either didn't know or were not very happy with her spending their inheritance like that. IDK that she was "rich", but certainly had lots of land in an area that was growing and building, and although was obviously "frugal" in her spending on herself (clothing, cars, etc) she was happy to shell it out to Jehover the WT Corporation.
Other significant donations were from successful members who were successful in business. Likely a good IRS write-off and made them look good (to those in the know) and feel good about themselves. The same ones who always wined & dined the CO/DO/Bethel heavies.
Those older ones were a major source of income for WT and they are dying off.
