petty theft vs pilfering

petty theft

noun
  • A theft of property having a value lower than a certain small amount set forth in a statute, and considered to be a less serious class of crime. 

pilfering

noun
  • The act by which something is pilfered; a petty theft. 

How often have the words petty theft and pilfering occurred in a corpus of books? (source: Google Ngram Viewer )