I agree that the overall numbers (if that is what's really important) show remarkable growth over the past 50 years. But perhaps the numbers of JW's is not the issue. The concern for JW leadership is retention of a faithful membership.
The last great influx of the general public conversions was in the late 1960's and early 1970's. These folks have children and grandchildren 'in the truth'. They are also at the age of retirement or older. The fastest growth within the organization is aging/retired ones. Or, that's how it appears if one 'scans' the local kingdom hall and assembly/convention population. What it really shows is a failure to retain the born-in Witness. In the United States. this is the reality of the organization's population. I hear it's reflected in Europe as well.
The organization is desperate to stop the apathy and disillusionment of it's members. These factors are their real enemy.