The parity policy was many of the European countries' efforts to get their currencies back to the same value in terms of price of gold as before WWI started in 1914. To do this they shrinked the money in circulation in society. This caused real interest rates to skyrocket, as money became extremely scarce. It bankrupted companies, farmers and landowners, while those who had access to cheap credit, for instance in the UK and the US (where the central banks expanded the money supply), as well as governments in the countries with the parity policy, could buy up land and capital at firesale prices. It's the same that ia going on today.