[iambibhas]

6-10% increase should be the normal sales amount variation, right? Any given month/week, this much of variation can occur without any reason.

[Evbn]

That's why multiple data points are used.

[AnthonyMouse]

There was only one shutdown. That isn't multiple data points. They could be measuring the effect of anything that occurred during the same time period as the shutdown: The recovering economy, which specific films were new releases during that period of time, the popularity of other goods or activities that serve as substitutes for movies during that period of time, the weather, etc.

To get multiple data points you need multiple events.