In the market, there are two brands of batteries of the same model. The price of the battery of brand A is 10% lower than that of brand B, and the former sells better than the latter. But the testing shows that the service life of the battery of brand B is 15% longer than that of brand A, but brand A sells better. The reason is that consumers do not know the difference in service life between the two batteries. In this way, in a competitive market, inefficient products that should have been produced less are produced more. This shows that incomplete information can lead to market failure.