That's the thing with a pseudonymous digital currency.
It is not knowable to you and me. The larger pool operators might be able to look at their withdrawals to see if they are being re-spent but there's no way to tell definitively if the withdrawal was for a hosted (shared) EWallet (e.g., Mt. Gox) or to the miner's local wallet.
With ASIC hardware, the bulk of the production cost has already been spent to acquire the hardware. Very little of the production cost will be electricity. This varied from GPUs where the inverse was mostly true.
If miners are indebted they will be needing to sell their production to repay the debt. It seems likely most ASIC purchases were not purchased with debt so it then seems likely most ASIC mining operators aren't really being forced to sell their mined BTCs whatsoever.