favorable vs unfavourable

favorable

adj
  • Standard spelling of favourable. 

unfavourable

adj
  • Of a belief, state of mind, etc.: not favourable; disapproving. 

  • Of wind or weather: causing delay or obstacles; not conducive to travel or work; inclement. 

  • Serving to hinder or oppose; adverse, disadvantageous, inconducive, unsuitable. 

  • Not auspicious; ill-boding. 

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