What is the average wage in the US? What is the median wage? Personal exemption?

The way I scope this out 1/2 of the working population earns under $22,000 a year. That's the median wage according to the information I found on the internet. After about $600 taken out for FICA and depending on the state state income tax and/or sales and other taxes on what's left there's an obligation to pay 15% federal income tax. The take home pay here then is about $16,000 or about $300 a week. That's a lot of people making some really low pay...Yet this is a 'rich country'? For 1/2 of the population it doesn't seem that way. Is this okay or am I not seeing somthing?