Well, but in same cases that doesn't happens !
Like I have seen some PR4 sites with Alexa of 1,555,555.
And also seen some sites with PR0 but Alexa 200K.
Simple curiosity. Most of the sites will be having comparatively related PR and Alexa Rating. Isn't it? Say if a site is having good alexa rating, It will be having good PR too.
So what should be an approximate alexa Rating for a PR1 site?
Yea, there is very little correlation:
1. Alexa ranking is based on visits by people who have the Alexa toolbar installed
2. Google PageRank is based on inlinks to the site
These two have very little in common.
Alexa is spyware and because of that, its not accurate.
Keep in mind, every time you post a thread or a question about alexa, your promoting spyware.
Is Alexa Spyware?
Build links for traffic and don't worry so much about PR. You will be mush happier.