low-quality vs subnormal

low-quality

adj

  • Of poor quality; inferior. 

subnormal

adj

  • Less than normal. 

  • denormal 

noun

  • A person whose abilities are less than normal. 

  • That part of the axis of a curved line which is intercepted between the ordinate and the normal. 

How often have the words low-quality and subnormal occurred in a corpus of books? (source: Google Ngram Viewer )