I think that the USDA does a great job in telling us what we may know, but just don't have the data to substantiate. While I already provided you with a link to the 2012 Ag Census, there are additional data that I think is interesting especially since it concerns beef cow operations.
The weather and feedstuffs price volatility have taken a toll on cattlemen the last several years. At several auctions, older cows brought $3000 easy; some as high as $4000. So one cannot blame cattlemen for deciding that it is time to leave the industry.
However, the data (see the graph from Beef Magazine) clearly demonstrate that the that from 1992 until 2012, the cow-calf sector has seen a decline of nearly 175,000 operations. The overwhelming majority (80%) of that decline (141,000 operations) has occurred within the category of operations maintaining 1-49 head of cattle.
Recently though I have seen new pastures spring up with cattle. While I do hope to even more people enter the cattle business, one must be pragmatic - cost of entering is astronomical. So potential young producers probably won't enter if they do not inherit land, cattle, and/or start-up funds.
Source:illinois.edu