In reaction to Sanders and Nee, Portes and Jensen make the clarification that those in ethnic enclaves need not be wealthier than those who left the enclave for the hypothesis to be supported. They instead assert that this will usually not be the case as the constant entrance of new immigrants into the enclave will actually be somewhat burdensome on the economy; a factor which does not actually represent disadvantage when compared with the other advantages provided. Additionally, Portes and Jensen outline three different conditions to be fulfilled in order to disprove their hypothesis. The first of these conditions requires the demonstration that ethnic entrepreneurship is a mobility trap leading to lower earnings than the immigrant's worth in human capital. The second condition requires data proving the work within the enclave to be exploitative, and the third condition requires data showing employment within the enclave leads to a 'dead end' and offers no chance of upward mobility. They acknowledge that the fulfillment of these three requirements is difficult as there is little data available to accurately test them.