Ergodicity: Difference between revisions

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=== Ensemble probabilities and time series probabilities ===
=== Ensemble probabilities and time series probabilities ===
In fact, the group as a whole ''won’t'' make money each round.
[[File:Ensemble vs time.png|frameless|left]]In fact, the group as a whole ''won’t'' make money each round.


Why? Because the ensemble average ''means nothing for any single player''. ''No one'' scores a constant 105% return. Players score ''either'' 150% ''or'' 60% and then invest their winnings in the next round. Their expected payoff through time is therefore not the snapshot ''average'' of the winning payoff and the losing payoff — that is a return the player certainly won’t get — but the ''product'' of the winning payoff ''multiplied by'' the losing payoff (i.e., 90%).
Why? Because the ensemble average ''means nothing for any single player''. ''No one'' scores a constant 105% return. Players score ''either'' 150% ''or'' 60% and then invest their winnings in the next round. Their expected payoff through time is therefore not the snapshot ''average'' of the winning payoff and the losing payoff — that is a return the player certainly won’t get — but the ''product'' of the winning payoff ''multiplied by'' the losing payoff (i.e., 90%).


This is the amount over time, each player should expect to win. Or, in this case, lose.
This is the amount over time, each player should expect to win. Or, in this case, lose:


This is the logic of the casino: the more you play, the more, inevitably, your investment will tend to zero.
This is the logic of the casino: the more you play, the more, inevitably, your investment will tend to zero.
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=== Salaries ===
=== Salaries ===
So, therefore if we all pool our resources and lead an anarcho-syndicalist community existence we will all be rich, rich, rich?
[[File:Ensemble vs time 2.png|frameless|left]]So, therefore if we all pool our resources and lead an anarcho-syndicalist community existence we will all be rich, rich, rich?


No. Put away ''Das Kapital''.
No. Put away ''Das Kapital''.
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=== The Bill Gates fallacy ===
=== The Bill Gates fallacy ===
All this is because, the snapshot average ''across'' a group of salaries doesn’t tell ''you'' anything about ''your'' own expectation through time. An “average salary” is an emergent property whatever group you choose to average: it is arbitrary. You can’t see it in any single salary.
[[File:Career expectations.png|right|frameless]]All this is because, the snapshot average ''across'' a group of salaries doesn’t tell ''you'' anything about ''your'' own expectation through time. An “average salary” is an emergent property whatever group you choose to average: it is arbitrary. You can’t see it in any single salary.


This is why, when Bill Gates hops on a London bus, he makes everyone on board, on average, a billionaire, even though 79 other people on the bus earn exactly what they did before he arrived and the bus average was £25,000.
This is why, when Bill Gates hops on a London bus, he makes everyone on board, on average, a billionaire, even though 79 other people on the bus earn exactly what they did before he arrived and the bus average was £25,000.
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That initial difference in money, after three years, is small in the context of a lifetime’s earnings: £31,000.
That initial difference in money, after three years, is small in the context of a lifetime’s earnings: £31,000.


But the compounding effect afterwards, even though both are making the same 5% return, is massive: after 40 years their salaries are nearly £100,000 apart, and over the 40 years, the aggregate earnings differential between them is £1.7 ''million''.
But the compounding effect afterwards, even though both are making the same 5% return, is massive: after 40 years their salaries are nearly £100,000 apart, and over the 40 years, the aggregate earnings differential between them is £1.7 ''million'':


Try not to have a slow start to your career, folks.
Try not to have a slow start to your career, folks.