Risk Homeostasis is a theory that humans have a certain level of acceptable risk and we will seek to keep that in equilibrium.
If we take high risk in one part of our life we will seek to minimise it in another part.
For example, in a Munich Case Study two groups of taxis were monitored for accidents. One group had ABS brakes installed, the others stayed with the regular breaks. You would think then that the ABS guys had less accidents right?
Wrong. What they found was the accident rate was about the same, the group with ABS having gained better braking would take other risks (ie braking late).