I assume you are referring to the growth rate of the Baha'i Faith. I am not sure what it has been in my local community, but I do not think it has grown much since I have been here, for about the last 27 years. I think that the Baha'i Faith grew faster in the United States in the 1970s and 1980s, you remember those days. I cannot say I know what happened after that or why it happened, but I sometimes think it could be that the idealism on those days we remember gave way to growing materialism which meant people were less likely to join a new religion that has idealistic teachings. But I do not think the growth in the United State is indicative of the overall growth, since the Faith has grown much faster in other countries such as India.
As I recall, there were five million Baha'is by the end of the first century, around 1963. There are approximately seven million Baha'is in the world now, so that indicates that the growth rate has slowed down since 1963.
It just so happens that I have written many posts on the "smallness" of the Baha'i Faith since an atheist on another forum continually ridiculed me about that, saying that proves that the Baha'i Faith is not true... So below is one of many posts I posted to him.
All religions grow slowly in the first few centuries.
How many Jews became Christians in the first century? There is no reason to think that the Baha’i Faith would be any different, because human nature has not changed. Every time a new religion is revealed by God, most people cling tenaciously to their older religions and nonbelievers are highly suspicious.
The Baha’i Faith is not doomed to failure just because it is still small in numbers, since numbers of adherents do not indicate failure.
The Baha’i Faith has endured innumerable obstacles since its inception. No religion in the history of mankind has undergone as much opposition as the Baha’i Faith did during the early years. Given all the tumult of the early years, it is amazing that it survived at all.
In spite of all the opposition, the Baha’i Faith was the fastest growing religion in the world from 1910-2010. Statistics show that from 1910-2010, the Baha’i Faith grew at a rate of 3.54%, whereas during that time Islam grew at a rate of 1.97% and Christianity grew at a rate of 1.32%.
Growth of religion - Wikipedia
The Baha’i Faith is a religion that is gaining prominence in the world. In spite of the fact that it is still fairly small it is recognized by governments all over the world.
Governments Recognize Baha’u’llah’s Bicentenary—Globally
The goal of the Baha’i Faith administration has never been to increase numbers of adherents but rather to expand to as many locations as possible around the world. These goals have been met. The Baha’i Faith has spread to over 250 countries and territories and is almost as widespread as Christianity. Most of this happened during the “formative age” of the Baha’i Faith (1921-1944)
FOURTH PERIOD: THE INCEPTION OF THE FORMATIVE AGE OF THE BAHÁ’Í FAITH 1921–1944
Now that this expansion has been successful, more recent goals are consolidation and community building as well as working with people of all religions or no religion on projects that are intended to bring about
the Betterment of the World. All these efforts have been successful and all Baha’i Fund goals have been met since the inception of the Baha’i Faith.