# Comparing two percentages when one is negative

I am having trouble comparing two percent values to show the change in one compared to the change in another.

For all stores looking at all sales:

The average sales growth for week 1 this year compared to last year = 8%

The average sales growth for week 2 this year compared to last year = 7%

Change:

$\frac{7\%}{8\%}-1=-12\%$

For all stores looking at only food sales:

The average sales growth for week 1 this year compared to last year = 25%

The average sales growth for week 2 this year compared to last year = 32%

Change:

$\frac{32\%}{25\%}-1=27.8\%$

So these values are the average total sales growth and total food sales growth this year compared to last for all stores. I want to compare a specific store to these averages:

For Store A looking at all sales:

The average sales growth for week 1 this year compared to last year = 33%

The average sales growth for week 2 this year compared to last year = 41%

Change:

$\frac{41\%}{33\%}-1=22.5\%$

For Store A looking at only food sales:

The average sales growth for week 1 this year compared to last year = 21%

The average sales growth for week 2 this year compared to last year = 47%

Change:

$\frac{47\%}{21\%}-1=122.5\%$

To summarize this all

All sales growth

Store A: 22.5%

All stores: -12%

Food sales growth

Store A: 122.5%

All stores: 27.8%

How do I compare the growth of store A compared to all stores for all sales and only food sales? What percentage of food sales make up all sales?

My first approach is the relative change formula: (new value - old value)/|(old value)

$\frac{22.5\%-(-12\%)}{\left |-12\% \right |}$ but since the base percent is negative the signs don't make sense

What about, $-(\frac{22.5\%}{-12\%})+1 = 2.8x$?

The values for food only

$\frac{122.5\%}{27.8\%} = 4.4x$

Does this make sense? Is the growth of food at this store compared to other stores 4.4x more? Is the growth of all sales 2.8x more at store A compared to other stores? Knowing this information, is it possible to look at what percentage of food makes up all sales?