new_premium = old_premium + (old_premium * percent_growth)
$16000 = $8000 + ($8000 * X)
$8000 = $8000 * X
1 or 100% = X
I get the way you state it and what is meant, I guess it seems an imprecise way to state it. I still think it would be much easier to state an increase of 2X (old premium is 8,000, new premium is x2 or 8,000*2= 16,000) - after all, it is at least doubling.