Another main concern in the literature is related to risk aversion. Adam Smith in early twentieth century postulated that if a job poses especially great health and safety risks, a worker will require higher levels of compensation for him to accept it. There is conflicting empirical evidence as to what extend immigrant workers are on average less risk-adverse than natives and voluntary accept riskier jobs to secure higher wages. Ávila (2009) found that Hispanic immigrants in the US with poor language skills tend to be pulled, rather than pushed into riskier jobs in exchange for higher wages. With opposed results, Kip Viscusi (2003) found that although differences in preferences could be influential, such differences cannot justify the empirical findings. He claims that immigrant workers face different wage offer curves as a consequence of having distinct labor market opportunities. Moreover, Hersch and Kip Viscusi (2009) in a latter paper found that Mexican immigrants incur into much higher fatality risks than US workers and do not receive wage compensation for these risks.