Income has gone down because jobs are paying less, duh. and why are jobs paying less? Because there is a larger pool of potential employees looking for jobs. As a result employers can offer less and those seeking jobs have to take it because they are desperate for the work and whatever wages they can get. What you think Obama has to do with that I am not sure. In fact, you should like wages going down as a result of the supply and demand principles that you usually trumpet so loudly.
And your link title? I'm sorry but do you think income would have gone up under McCain? I highly doubt it. Even if the economy began to pull out of the recession at a quicker rate I highly doubt wages and thus income would go up (at least much). The simple fact is that the pool of resumes is too big and there isn't enough work to go around to cause enough competition to force employers to offer more.
Just think, if the government hadn't stopped the collapse of our economy with the bank and auto bailouts there would be thousands and possibly millions more out of work making that resume pool even larger and driving wages down even further. But you were against those bailouts so I guess that means you ARE for driving down wages and income.