Here is a simple explanation of how inflation happens with the current system (Please excuse run-on sentences):
When an item is sold to the server shop, a new player joins (initial balance), someone wins gets a reward and gets money from a job; money is created. When an item is bought from the server shop, someone is fined, Playertaxes or a player quits, money is destroyed. For each shop transactions, only a small amount of inflation or deflation will occur and usually balance out, but this system has some major flaws which is the reason shop prices change. For example, say I farm spiders for 3 days straight and sell $11,059,200 worth of spider eyes (actual statistics if earning 64 per minute and grinding for 72 hours); this creates more substantial inflation. Now, money is worth less and items cost more. Now, to find the amount of inflation you will need to use this equation: I = (S + N + R + J) - (B + Q + F + P) [I = Inflation, S = Sold to Shop, N = Initial Player Balance, R = Rewards (Vote/ Contest/Reaction), J = Money Earned From Jobs/Paychecks, B = Bought from Shop, Q = Quit Player Balance, F = Fines, P = Playertaxes]
Now to find the amount of inflation in a ratio from the Initial Amount of Money in the Market (The amount of money which will be your base of measure, this can be at any time, but to find the total amount of inflation, you will need to have this as the original amount of money on the server):
T : 1 as I : X [T= Initial Amount of Money, I = Inflation, X = the comparative of interest]
To find X you will need actual values, so here is an example; T = 1,000,000; I = 100,000 | T= 1; I = 0.1
So Inflation is 0.1. Now this 1 and 0.1 are the currency I need, but can't find.