The interesting thing about the graph is, as far back as it goes, the contributors fluctuate but seem not unusual or unexpected. So companies are not extraordinarily greedy right now, they act the same as ever, just more do so.

My personal, uneducated, unverified hypothesis was that companies overcompensate price increases for three main reasons:

* They assume consumers dislike many small price increases. The current increase, therefore, has to last until the next oportunity.

* They expect an economic downturn, and want to extract as much money in preparation of the reduction (ironically fueling the downturn).

* They use the opportunity to adjust to what they expect the market would accept, because they assume PR backlash if they do it without a reason.

I think the last one is a form of "market inefficiency" but one that generally benefits consumers.