I have the sentence:
The figure grew steadily since its six-month ___________.
So I'm looking for a word to complete the thought, given that this statistic/figure has been in existence for six months. I had thought of "inception" or "half-life" but these choices seemed to be kind of stretching it.
Question
What is an appropriate word choice for my example sentence? Need to sound formal/professional, but not necessarily high-syllable.