What is the benefit to average families of the decline in oil prices?
One of the many benefits is a $2000+ annual savings via the lower price of gasoline.
This assumes a 2-car family, driving each vehicle 15000 miles per year, and a $1.50 drop in the price of gasoline from the roughly $4 per gallon price peak of the past. Feel free to adjust the assumptions, but this looks pretty close to what happened. Thank you fracking (plus a few other lucky developments).