How much rep is required to get a second rep bubble?

[Sun]

How much rep is required to get a second rep bubble? I'm sure a lot of us have been wondering this. I noticed that a bunch of my Forum Game buddies have 2 rep bulbs. How much rep is required to get the second bulb? 50 points?

[OrbitusII]

Each bubble represents a range of 100 points. For example, 0 bubbles = 0 points of rep, 1 bubble = 1-100 points, 2 bubbles = 101-200, etc. I have 171 points of rep, hence my two bubbles.

[vexx32]

And I have 387 points, thus four bubbles.

It changes a bit once you reach 500 -- each one after 500 represents 200 rep each and is coloured light green.