How Many TH/s were on the network before ASIC mining arrived?

[bitcoincasinosupport]

I'm trying to deduce how many TH/s the network expects to lose (approx) when GPU Miners drop off due to ASIC competition and network difficulty rise.
Because at some point soon, everyone mining with GPU will be losing money.
Anyone care to take a stab at this?
Or has it been done already, and if so, can someone point me there?

Thanks! 

[SgtSpike]

Somewhere between 25 and 35 TH/s IIRC.

[os2sam]

I think it was around 22 to 24 THs.  GPU Mining had increased dramatically as well at first too because the Bitcoin price skyrocketed too.