• by Sarah Mahoney  @mahoney_sarah, July 20, 2009

Looks like Wal-Mart Stores' recent plan to develop a sustainability index that clicks with consumers will arrive in the nick of time: A new study finds that when it comes to giving information about green purchases, consumers give retailers a D-.

Overall, close to 40% of consumers in all segments say the information that most stores provide about green products is insufficient, with Gen Y shoppers the most dissatisfied, reports Miller Zell, an Atlanta-based retail consulting firm. "Shoppers want to be assured that they are getting what they are paying for," the study reports, "and they want to know exactly what the 'what' is." Results suggest that most green claims are used too broadly, leaving consumers uncertain about the environmental advantages of their purchases.

The study, which tracked about 1,000 shoppers, also found that a startling 50% of all shoppers say they are willing to pay as much as 10 cents more for a green product, with low-income shoppers most willing to do so. (Some of that is likely due to the heavy green leanings of Millennials, many of whom are just entering the workforce; 62% of the Gen Y respondents are willing to pay more for a green choice.)

Women are also more likely to be willing to pay 10 cents more, while high-income respondents, men and Baby Boomers were least likely to do so. Curiously, high-income people were most likely to say they would pay up to 30 cents more for a green product.

In terms of store types, grocery and mass are the channels where most shoppers expect to purchase green products, which means there's plenty of room for other types of stores -- especially department, electronic and specialty retailers -- to differentiate themselves with environmentally inspired offerings, displayed in a way that provides enough information to satisfy curious shoppers.

The survey also finds that stores could be doing much more to boost impromptu purchases: 62% of shoppers say they are likely to pay more for a green purchase when making an unplanned buy.

Last week, Wal-Mart announced plans to develop a worldwide sustainable product index with 1,500 suppliers, which will establish a single source of data. "Customers want products that are more efficient, that last longer and perform better," Mike Duke, Wal-Mart's president and CEO, said in making the announcement.

"And increasingly, they want information about the entire life cycle of a product so they can feel good about buying it. They want to know that the materials in the product are safe, that it was made well and that it was produced in a responsible way."