Before you say that :In conclusion, domain age is not a factor to rank a site.
2 other sites have Alexa Rank of 20,000 yet in Google search they are below the top site. These are more international directories so have more visitors from US for example and thus a lower rank.
The top site is UK based companies only - again it shows in Google.com,.fr.de etc. on the first page at least
The Alexa rank should only be used as a guide.