An increase in consumer income will shift the demand curve for an inferior good to the left. Think about it this way. If people work provide a service, like a job or a service, then it makes sense that when people buy things they want to buy high quality items. No one wants to buy something they worked hard for on things that do not last.
Therefore it makes sense that people would rather save up their money to buy something they feel is a higher quality and deal without the item for longer. After all, they have never had the item so they will not miss it while they save up money for a more expensive one.
An increase in consumer income will shift the demand curve for an inferior good to the left. The more people that money have, the more that they may purchase things. They do not want to just purchase items. They want to purchase quality items.
This means that they may steer clear from lower-priced items as they may view these as inferior as compared to the ones that they can get with the income that they have. The truth remains that people will purchase what they can afford. Yet, there are also some people who purchase items beyond their means simply because their income has gotten higher.