Introducing new goods into your market will help you diversify your economy and alleviate the demand for crucial industrial goods. It will also give Pop's more choice in their spending of Wealth.
Some goods are favored by Pops over others by default if available. Once Electricity is available to them, due to its convenience Pops will prefer to buy it over Wood or Coal, even if they’re the same price. Some goods can be replaced by other goods entirely, while others will always be required to some bare minimum. Of course, that is if they can afford it. Many Pops will only be capable of affording, and will therefore need, only the Basic Goods.
Train travel can completely replace the need for having your own Automobile to drive around in, but having an Automobile doesn’t ever completely remove the need for an occasional train ride to see your cousin who lives all the way in Paris.
Importing Oil, either petroleum from newly discovered deposits or whale oil from the few places in the world that produce it will cause your Pops to buy some quantity of it for heating instead of Coal or Electricity, which lowers the price of those goods and help make your industries more profitable. Introducing Opium into your market will decrease Pop demand for Liquor and Tobacco, for good or ill.
Paradox Interactive
In addition to these factors, cultures can develop Obsessions for certain goods, and some even have Taboos they must abide by. A country can also encourage or discourage the consumption of certain goods using Authority, perhaps in an effort to avoid enriching a hated enemy or entice Pops to buy something that’s heavily taxed over something that is not. This impacts the purchase habits of Pops affected despite this being irrational from a strictly financial perspective.
All of these, of course, influence the Economy, which in turn affects the prices and Pop wealth, then supply and demand, and makes a full circle once again. Just make sure not to import something that will replace what your own country is producing.
