This work resulted in their jointly authored publication Incomes from Independent Professional Practice, which introduced the concepts of permanent and transitory income, a major component of the Permanent Income Hypothesis that Friedman worked out in greater detail in the 1950s.
Ovo djelo je rezultiralo njihovim zajedničkom publikacijom "Prihoda od neovisnih stručnih praksi", koja je uvela pojmove trajnog i prolaznog dohotka, glavne komponenta u računu i hipoteze stalne dobiti koje Friedman razrađuje detaljnije godine 1950.