The Obama responsibility period began this week

With exactly two years since Obama's inauguration having passed, I'm somewhat arbitrarily picking this as the time where his administration bears greater responsibility for anything done well or poorly by the executive branch than any previous administration. Credit and blame can be adjusted on a case by case basis - for example, Bush bears more responsibility for 9/11 than Clinton because he downgraded counter-terrorism efforts - but as a general matter this makes some sense to me.

A different question is when the current administration bears more responsibility than all previous administrations combined. I'd give about four years for that one.

I realize these are somewhat unfair and rushed periods, saying that a president has the responsibility to fix the mistakes of previous 200 years in four, but it's not supposed to be an easy job.