After about 3 months of torture, or the whole summer that is.  The problem about level 20 was that you mainly gain only 1-2% at most per day, and on some occassions 3%.  I'm glad I'm finally past the dreadfully slow level 20, because the next levels are sure to be faster (I noticed once I reached level 21 that it went up 5%, I was at 99% the previous day at level 20).  If any of you reach level 20, I must warn you that it is 1 of the slowest levels on GS, and I've pretty much reached a milestone by passing it.