Find out if increase in a series of values is statistically significant

Let’s say I have a series of previous year’s weekly sales for a product ${x_i}$ and the series of sales for the same product this year ${y_i}$. How can I find out if the increase in sales are statistically significant?

Edit: Context: I have weekly sales of a group of items for the previous year. We ran a marketing campaign for that group and again recorded the weekly sales for the current year. I want to know whether running the campaign had any significant impact on sales. I’ve seen answers related to changepoint analysis, but I don’t think that applies here. The item sales need not necessarily form a time series fit for regression and all. Since I want to get the broad impact of the campaign of sales on those items, I’m not worried about item-level impact.