at a premium vs in short supply

at a premium

prep
  • Scarce, in short supply. 

  • At a high, or higher than expected, price. 

  • Above par value. 

in short supply

prep
  • scarce, or difficult to find, or buy. 

How often have the words at a premium and in short supply occurred in a corpus of books? (source: Google Ngram Viewer )