To answer the titular question of this article: more than you might think. Reading labels is an important step in the purchase of food, beverages and dietary supplements. However, there is a significant gap between how much Americans think they read on nutrient labels and the amount of information they actually absorb.

A study published in the Journal of the American Dietetic Association found that consumers tend to read just the top five lines of a product’s nutrition information. Researchers also determined that participants were more likely to read this information if it was placed above the product description and its price, rather than below or to either side.

Scientists came to these conclusions after presenting more than 200 volunteers with sample product labels. Each participant was fitted with an eye-tracking device. In all, more than one-quarter of all volunteers reported reading the entire nutrition label.

How many actually read the whole thing? According to the research team, it was just 1 percent of participants.

“Because knowing the amounts of key nutrients that foods contain can influence consumers to make healthier purchases, prominently positioning key nutrients and labels themselves, could substantially impact public health,” the authors concluded.