Facebook may have access to your income information through various means, including:
Self-reported income: You may have provided Facebook with your income information when you signed up for an account, or when you filled out your profile information. This information is usually voluntary and can be used by Facebook to target advertising to users who fall within a certain income bracket.
Third-party data: Facebook may also obtain income data from third-party data brokers and marketing firms. These firms collect and sell consumer data, including income data, to companies like Facebook, which use the information for advertising and other purposes.
User behavior: Facebook may infer your income level based on your online behavior, such as the types of pages you like, the ads you interact with, or the products you purchase. Advertisers can target users based on certain behaviors that are associated with a particular income bracket.
It's worth noting that Facebook's use of personal data has come under scrutiny in recent years, and the company has faced criticism for its data collection practices. If you are concerned about the use of your personal data, you can take steps to protect your privacy, such as adjusting your privacy settings or limiting the amount of personal information you share online.