On the formulae page of the wiki it is stated that the losses for changing governments are:

NW < 10.5M: 14% losses
12M < NW < 30M: (14+25*(NW-10.5M)/18)% losses
NW > 30M: 39% losses

But shouldn't the 12M be 10.5M as well? Or is there a third formula for 10.5M < NW <12M that is not on the page?

There's the part where you deduce whatever your current NW is by 10.5m, and if you put in 10.5M nw you'll lose exactly 14%.

One funny thing is, if you put 30m nw in it, you'll lose 41% instead of 39%, while if you put in 28.5m nw you will lose exactly 39%.

So I believe the correct formula should be:
10.5M < NW < 28.5M: (14+25*(NW-10.5M)/18)% losses
NW > 28.5M: 39% losses

Someone with that sort of NW should be able to confirm here.