DislikedQuantity of money (Q), Velocity (V)
Q x V = X
2Q x 1/2V = X
I'm not exactly sure what 'X' is. But I guess the above shows an increase in Q doesn't have to have any effect as long as V decreases enough too. Saying that, this is probably the equivalent of 'bar napkin calculations'. :/Ignored
In any event, this really misses the point. All the "money supply causes inflation" arguements are predicated on an assumption that Q+ / P = D+ = I. In other words, when you increase the quantity of money (Q), the amount available for each member of the population (P) is increased. When each P has more money, they are able to demand (D) more of all the resources in an economy. That in turn reduces available supply and produces inflation (I).
The problem with this arguement is that those who advocate it can't explain how the increased Q gets into the hands of P. Last time I checked, there were no helicopters dropping suitcases full of money into the streets...
Once you start trying to explain the intermediation mechanism, you realize that the amount of Q in the system is irrelivant. I'm not going to go into all the details of the process, but the long and short is, the fed can't "create" money. It can only exchange assets. For every dollar it prints, it destroys $1 worth of other assets, so the net impact is zero.
In the real world the money supply is nothing more then a lubricant greasing the wheels of commerce. No matter how much (or how little) of it there is, the variable rate at which it changes hands (velocity) ensures there is precisely enough for the economy to function.