Suppose that we had a base 8 system instead of base 10, perhaps because, in this hypothetical world, we had 8 fingers rather than 10. Would we pay 1/8 our increase, or do you think it would still be one tenth?
Or, to reverse causality, what are the chances we have ten fingers so that we’d develop a base 10 system that would make it easier to count out our tithing?
Now suppose tithing were 12.5%, a 25% increase. What fraction of current tithe payers would stop paying? This would be the “price elasticity of tithing”. What about if tithing were 20%? What about 8%? From a typical economic framework, one would say that God decided the fraction tithing we pay based on maximizing some outcome he desired — presumably salvation– and likely made it what it is because it optimally balanced some societal average of our willingness to sacrifice and the benefits from that sacrifice.
If a society’s income went up by 20%, would more people pay a full tithe, or fewer? The change is called the “income elasticity of tithing”. If full tithe paying rises, than tithing would be what is called a “luxury good” — you spend a higher fraction on it as income rises.