In a market economy the production is determined not by someone's decision (which can be wrong, and a wrong decision is the reason why there there are unwanted goods or a lack of wanted goods) but it is regulated by the supply and demand: if there is a need for a good, it will be produced, and if there is no need for something, its production will halt and there will not be an unwanted storage.
In short, in a market economy, the economy itself regulates this.
