Customer loyalty is about much more than repeat purchases—especially in insurance, where one person only needs so many policies.

You’re always looking for new customers to grow the business, while also focusing on retaining current ones. And if you’re like most independent agents, you’re doing this without a team of dedicated marketing professionals.

What if you could ask one question of your customers to boost business?

Well, you can: “What is the likelihood that you would recommend Agency ABC to a friend or colleague?”

This one question is used to calculate your Net Promoter Score (NPS)—a customer loyalty metric developed by Fred Reichheld in his 2003 Harvard Business Review article “One Number You Need to Grow.” NPS is a best-practice method of collecting data from current customers to determine strengths and weaknesses.

According to Reichheld and Bain & Company, the creators of NPS, NPS leaders grow, on average, at more than twice the rate of competitors—and a high NPS correlates strongly with repurchases, referrals and other actions that contribute to growth.

How can you collect NPS data about your agency? To simplify the process, create a form on your website that asks customers the above question, allowing them to answer with a single number from 0 (not at all likely) to 10 (extremely likely). Include one additional question asking customers why they gave you that number.

At the end of each quarter, review your data and calculate your NPS. Based on the numerical answers collected from customers, you can categorize them into the following groups: Promoter, Passive and Detractor.

Promoters are your cheerleaders. They respond with a 9 or 10 and are very likely to recommend you.

Passive customers respond with a 7 or 8. They aren’t negative about your company, but they aren’t actively talking about you either.

Detractors are customers who respond with a 0-6. Let’s just say these customers aren’t leaving you any five-star reviews.

To determine your agency’s NPS, simply take the percentage of promoters minus the percentage of detractors. Scores range from -100 to 100. The higher the score, the better.

Determining your NPS score is important because it gauges your customers’ overall feeling toward your agency. It also helps determine whether your customer experience is positive or has room for improvement.

If your NPS score is low, it’s time to plan tactics for improved experiences. If it’s high, you know you’re on the right track. And don’t forget—a good NPS is a marketing tactic for attracting new clients!

Katie Gouldner is PR and marketing communications specialist at Millers Mutual Insurance, a property-casualty insurer protecting small and midsize businesses in PA, DC, DE, MD and VA through a network of independent agents.