There is a coin in your pocket right now, and there is an identical coin in someone else's pocket across town, and those two coins are worth different amounts. Same metal, same stamp, same date. The difference between them comes from how each coin arrived. One of them was spent early, while prices still belonged to yesterday. The other arrived late, after the prices had already risen to swallow it. That gap, between the coin in the nearest hand and the coin in the other pocket, is the subject of the book I am holding today.
