How do you determine if the percent growth between two time periods is statistically significant? For example, the total population in 2000 was 180,000. It grew to 220,000 ten years later. How do you determine if this 22% growth was significant? Similarly, group A (6,000 people) earned £50,000 last year. Group B (9,000 people) earned £65,000. Are Group B's 50% earnings over Group A statistically significant?
I think you are confusing "statistically significant" with the common sense of the word "signficant" which means "important" or "material". I always try to avoid that use of the word around statistics, and generally opt for "material" instead. "Statistically significant" is short hand for "statistically significant evidence against the null hypothesis". Statistical significance only matters when you are conducting some kind of inference; not when you are just describing census data.
Think if you have a historical data (sufficiently large) for YoY growth rates, you can spread them out and see what are the chances of the growth rate happening. If the data is large then you may normalize the data by subtracting the mean and dividing by the standard deviation, now plot the distribution and see if it lies towards a tail. Ex: It may well happen that it takes a bell shape and your value lies in a tail.