Inflation is usually measured in relative numbers. Relationships always require a point of reference.
For this purpose, data for the previous year for the same period is most often used.
But now we've come to the point where it doesn't work.
If we have a sharp spike in data, then the attitude to this data shows a distorted picture.
Today, the picture of weekly inflation looks like this.
It is clear that the attitude to spike data does not mean anything.
Therefore, we need to use weekly data and present it as an annual growth rate.
Since the numbers have some fluctuations, we can somehow average them.