Why 400 points in 400 days is exceptionally much

I have tried to reconstruct the rating of Kasparov during his youth by researching his autobiography "high play".

Age Rating Fact
05 1300 Learned the game
06 1400
07 1500 Started with lessons
08 1600
09 1700
10 1800 Botwinnik-school
11 2000
12 2100
13 2200 Candidate master, first tournaments abroad
14 2300 Master
15 2450 First victory over a grandmaster
16 2545
17 2595 2nd grandmaster result
18 2625 Grandmaster

So even a very talented player like Kasparov grew only at average 100 points a year!

Two years of tactical traning improved my rating from 1532 to 1701, about 170 points.
In this period I solved about 10.500 tactical problems.
Which is about 62 problems per ratingpoint.
I didn't repeat the problems.

Now I'm plateauing during a year.
Inspired by de la Maza I started to repeat problems now a seven times.
This new approuch seems to work. My results OTB are very good at the moment. If I don't blow things the upcoming games I'll leave the plateau of 1701. Which we should know at 1st of may, when a new ratinglist arrives.