In addition, standard errors are clustered at the state and year level to account for the possibility that observations within states and across years are not independent. The idea being that theoretically the NLC should not have an impact on intra-state job flows since the NLC does not offer added advantages for nurses to move within a given state. Another sensitivity test involved analysing the impact of the NLC from treated to control states, with the idea being that a nurse in a Compact state should, in theory, not be compelled to relocate to a non-Compact state once the NLC is introduced in his or her resident state.