Most unemployed people often turn to petty crimes and sometimes big crimes such as robbery, prostitution and drug-trafficking.

petty 是形容词，意思是"小的、轻微的、琐碎的"，常用来形容不重要或不严重的犯罪行为。petty crimes 指那些相对轻微的违法行为，比如小偷小摸、轻微欺诈等。