But foreign funds are largely spent upon things which, however excellent they may be in themselves, are not really _necessary_ for the religious life of the Christians, such as missionaries' salaries, high schools, colleges, medical institutions, and expensive buildings.

Consequently to know the total expenditure in the area is not to know the necessary expenditure.

The native Church might maintain its life and conquer the whole district without spending in actual money a tithe of that which we spend on providing the people with medicine and education and buildings and foreign missionaries.
Yet the question cannot be avoided.

Missionaries all over the world carefully count every penny which the converts subscribe, and search diligently for some new method of doubling it, in order to lead their converts towards the goal of self-support.

What that goal is we do not know.