What is the primary attribute measured in percent decrease calculations?

Percent decrease calculations focus primarily on the change in value, which reflects how much a quantity has reduced from its original amount. This measurement is crucial for understanding the extent of decline in a particular metric, such as sales, prices, or any quantitative assessment.

To calculate the percent decrease, one determines the difference between the original value and the new value. This difference constitutes the change in value. The percent decrease is then found by dividing this change in value by the original value and multiplying by 100 to convert it into a percentage. This method allows for a clear understanding of the relative size of the decrease in comparison to where it started.

In this context, the other choices do not serve as the primary focus of percent decrease calculations. Sales tax is irrelevant to the concept of percent decrease, as it pertains to tax calculations rather than value changes. The original value is necessary for the calculation, but it doesn't represent the change itself—it's the baseline from which the decrease is measured. Similarly, while the new value is important in determining how much has decreased, the percent decrease specifically looks at how the original value has changed to arrive at the new figure. Hence, the focus is on the change in value.