According to some textbooks, the specific growth rate is the highest during Log phase. However in my calculation, the specific growth rate is the highest just after lag phase. To calculate the sustainable growth rate, start by dividing your sales by your total assets to get the asset utilization rate. For example, if your sales are 25,000 dollars and your total assets are 100,000 dollars, your asset utilization rate would be 25 percent. During puberty, growth rate increases again to a second maximum, after which it slowly declines to zero. This is typically referred to as the pubertal growth spurt. On average, female and male growth trails off to zero at about 15 and 18 years old, respectively.