What consonant is often substituted for the ‘th’ sound? What other language related to English does this take place? For a bonus point, what is this Law called?

The great depression, which lasted throughout the 1930s in the united states, affected many people, and it had a devastating impact on an entire subset of the u. s. population. modernist writer john steinbeck wrote about the toll the depression took on these families, many of whom were forced to leave their farms and find other sources of income.