Trade
From Captain of Industry Wiki
On the world map, other villages provide quick trades, or a more long term trade agreements. This way, the player is able to gain an infinite supply of other materials, thus making even the initially non-renewable resources like iron and copper fully renewable. Currently, the game world will always contain the same trade offers with the same item ratios, and only the position of the trading villages is randomized at the start.
The quick trades start off at a base line ratio, e.g. 20 Wood for 20 Concrete blocks, but with every two trades the trade ratio worsens by some amount.