Which topic is explored in the intercalary chapters in the grapes of wrath

The intercalary chapters in Steinbeck’s Grapes Of Wrath serve as a literary device designed to show the general social and economic elements of America at the time. Due to the economic crisis plaguing the nation, the plight of the American farmer became increasingly difficult. The contrast between the regular chapters and the intercalary chapters serves as an illustration of the part to whole relationship between the Joad family and the American farmer.