Your kidneys are complex organs. They regulate the amount of water lost from the body and get rid of waste products, especially urea. Urea is made when any excess amino acids are broken down in your liver.
Middle Class Income for a Family. The annual average income for a middle class family of four is approximately $70, 354. This is based on a 2006 report by the U.S. Census for a family of four. This figure is in the middle of the range of incomes for this section of the population. The median income during this time for all households was $48,561.
If you are in the top 20% of income earners, you are considered to have an upper class income, or be rich. Those whose incomes fall in the bottom 20% are considered poor. Everyone else (the middle 60%) is middle class. Income Range: There are some economists who say that anyone who makes between $25,000 and $100,000 a year is middle class. That might be surprising to some, though. Median Income: Others take a look at the median annual income, and then go $20,000 to either side.