Unless stated otherwise numbers are for Mainline Christians in America.

80/20 Rule:
The "80/20 rule" or Pareto Principle in a church context suggests that 20% of the congregation often contributes 80% of the ministry work or financial giving.

US Church Attendance:
2024 Gallop: Among major U.S. religious groups, members of The Church of Jesus Christ of Latter-day Saints, also widely known as the Mormon Church, are the most observant, with two-thirds attending church weekly or nearly weekly. Protestants (including nondenominational Christians) rank second, with 44% attending services regularly, followed by Muslims (38%) and Catholics (33%).


Giving:
I couldn't find any good number on giving units per member.
You would assume giving units per member would be about 50% assuming a giving unit would be a couple.
But the membership of most mainline churches is getting older and has a higher percentage of single women, so it might be higher.

Links:
US Religion Stats


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