Jane Jacob's economics thought is often condensed as something called "import replacement." More accurately it can be said to be summed up as an economic self-replicating ecosystem. Better yet, as "new work added to old." Her hypothesis in The Economy of Cities is that there are three ways, and only three ways that she was able to uncover, by which a city's economy grows and prospers—"
• By adding export work to other people's local work; • By adding export work to different local work of their own; • By exporting their own local work."
"The significant fact about these processes is that they all depend directly on local economies... these are the only ways I have been able to discover. Indeed it soon becomes exceedingly tiresome to read the business histories of exporting organizations because their narrative plots are so few. One might be reading the same three novels over and over again." Chapter 6, How Large Cities Generate Exports.