When it comes to making purchasing decisions, U.S. shoppers want to answer them in the space of a quick glance. "How much does it cost? How much do I get? How well does it work?" Now, according to a new survey, marketers have to answer one more question during that glance: What does the product do for the planet and for people?

More than 80 percent of U.S. shoppers want a single sustainability rating for all products that 75 percent say should be displayed as a numerical score and produced by an independent organization with no profit motive, according to One Green Score for One Earth.

The research white paper was released by Ryan Partnership Chicago, a marketing firm that works with large brands including Chase, Nestle Waters and SC Johnson; and Mambo Sprouts Marketing, a marketing company focused on the natural and organic sectors that does market research and produces coupon books for retail outlets.

Sustainability in the marketplace, "is near a tipping point," the paper's authors wrote. It is so pervasive that, "Even those who say sustainability is not important to them … estimate that about one-third of recent purchases were sustainable," according to the paper.

People interested in buying green products define them differently than manufacturers and retailers do, the study found. Although environmental impact is a key aspect of sustainability for respondents, many also cited social issues. Nine out of 10 "Light Green" respondents agreed that three items -- quality, healthiness and environmental friendliness -- are important pieces of that definition. "Heavy Green" respondents said 12 factors are key to the definition for 90 percent of them. The chart below lays out the factors ranked as most important for "Heavy Green" respondents (click the image for a larger version).

Corporate interviewees tended to hew closer to the traditional definition of helping -- or at least not harming -- the environment for a definition of green. Increasing energy and supply chain efficiency and the resulting cost savings are corporate America's big markers of being a good corporate citizen, according to One Green Score for One Earth.

With such a difference in how sustainability is defined, it's no surprise that the public says it wants a single score that encompasses all aspects of sustainability stamped clearly on each product or at least on the shelf below it. About 80 percent of those "committed" to buying green products say such a score would influence their buying decisions, the researchers found. Even 55 percent of those claiming that buying sustainable products doesn't matter to them support the idea of one clear sustainability score.

There's no easy way to come up with a clear numerical score for sustainability that can be applied to all products and satisfy all parties. At least 75 percent of each type of respondent said an independent, non-profit organization should develop and oversee the scoring structure, yet "leading edge manufacturers and retailers committed to sustainability stressed the need to be at the table to ensure that the sustainability score is realistic and is something that can be implemented."

However it happens, it's vital to develop an easy way to quickly get a product's impact across, the paper says. "As the industry comes to terms with how to communicate sustainability in a way that is useful to shoppers, it is critical that we understand what they (shoppers) want to know," its authors said.