Ok but as I understand their argument no country can perpetually rely on those things and that it was governments that helped spur growth in areas in these non-agricultural sectors.
Their point being that simply exporting agricultural goods means that from a competitive point of view, you will eventually get competition and that when it comes to agriculture it is easier to enter and dilute the market. Therefore even a sophisticated agricultural economy would not be able to match a manufactoring economy(19th century context) in terms of creating wealth.
