What factor attribute to Chance of Gems upgradable %?

[stud4fun]

My bot has rank 5- rank 8 gems and only 2 gems has rank 30 and 31.

Now my gems has 0% or 1% upgradable chance even rank 8.

Does anyone has insight of which factor contribute to chance of upgradable %?

 

[botti]

Google is your Friend - diablo3 gem upgrade chance

 

[stud4fun]

Google is your Friend - diablo3 gem upgrade chance

hmmm. you're right

 

[Winchester]

Google is your Friend - diablo3 gem upgrade chance

lol