Before revision:  The relaxation time scale of the population to its steady state is determined from the distribution of single-cell growth rates independent of the details of the division process . We propose an experimental method to measure single-cell growth variability by observing how long it takes for the population to reach its steady state or balanced growth.
After revision:  The relaxation time scale of the population to its steady state is determined from the distribution of single-cell growth rates independent of the details of the division process such as the noise in the timing of division and the mechanism of cell-size regulation. We validate the predictions of our model using existing experimental data and propose an experimental method to measure single-cell growth variability by observing how long it takes for the population to reach its steady state or balanced growth.