Brand loyalty is defined as a consumer’s preference for a particular brand and a commitment to purchase that brand repeatedly in the face of other choices. But in today’s world, we find ourselves less loyal to the brands we buy and loyal to fewer brands. Our first question is “Do I want or need it?” Increasingly, the answer is: no. Consumers have been stocking fewer brands year over year since 2006.

While it is easy to blame the economy, the real question we need to ask ourselves as retailers, brand marketers and agencies is: Are we being loyal to our shoppers — or only to our shareholders?

To gain some insights into these questions, the Hub surveyed its loyal readers — a geographically dispersed, slightly skewed representation of the general population — to understand their preferences and commitment levels across 19 categories. After reviewing more than 250 pages of responses, it is clear that loyalty is primarily driven by product quality and customer service.

Product quality is the cost of entry for any brand. While some respondents use superlatives like “extraordinary,” most described the brands they were loyal to as having good, dependable quality, which for the price delivered a solid value proposition. They described how their favorite brands evolve with thoughtful, innovative features that are authentic to the brand and address their needs.

Winning brands are also supported by helpful, friendly, fast, personal support, which makes the individual shopper feel valued. Such service is backed by no-hassle warrantees and guarantees that reinforce the marketer’s commitment to its brand. By aggregating brands into broader categories, we can see which components of both product quality and service really drive loyalty.

Retail. Combine home improvement, hardware, drug and club into a “retail” category and we see that product quality is defined as having a broad (but not overwhelming) selection of quality products at a good value, merchandised in a clean, familiar, easy, convenient and fun-to-shop experience. But the real loyalty driver is convenience — said another way: location, location, location. Other features that reinforce convenience also rise to the top, such as Walgreen’s prescription notification service and drive-through window.

The benefits of being loyal to a core shopper come through for a couple of retail chains: Lowe’s focus on female shoppers has driven loyalty with that target, while Home Depot is winning with the professional-contractor audience. Costco shoppers gush over the product selection and service.

In an increasingly crowded retail marketplace and in the absence of true differentiation, shoppers are consolidating trips to achieve time and dollar savings. For other classes of trade, survey respondents described retailers as being “interchangeable,” or increasingly replaceable by another class of trade.

Lifestyle. When we aggregate apparel, music and automobiles into “lifestyle” brands, loyalty drivers center on how a brand’s products, quality and customer service best align with the shopper’s personal style and value proposition. Success in these categories hinges on knowing and delighting core shoppers. Since style is so personal, respondents were quick to write in their favorite brand which “fits who I am.” In sports apparel, for example, the definition of personal style is extended to include the athletes, teams, or sports that the shopper supports. Authenticity wins.

In the automotive category, if affordability and dependability were core values, survey respondents were most likely to favor Toyota, Honda and increasingly Subaru and Volkswagen. Those who value performance and aesthetics often selected BMW or Mercedes. However, many readers voiced support for American-made cars, which have enjoyed an increase in product quality, as well.

Services. On the flip side, when we group cell phone carriers, credit cards, shipping companies, car rentals and hotels into a broader “service” category, we see price and convenience as key drivers. Often this shopper behavior was fueled by online services, which are quick to identify the closest and cheapest options.

For services, differentiation and loyalty are often driven by rewards programs, value-added services or exclusive products: Hertz Gold Member Service, Marriott Rewards, AT&T’s iPhone (for a while, anyway) and Enterprise’s pick-up service, for instance.

What’s most interesting is that for cell phone and credit-card companies, the perceived cost and complexity of switching services often maintains shopper loyalty, albeit because of inertia.

Packaged Goods. Consumer packaged goods have definitely taken a loyalty hit in the past year. A study by Catalina Marketing Corporation reported that only four out of 10 brands held onto at least half of their highly loyal customers between 2007 and 2008.

Not surprisingly, in a world where private label is gaining acceptance, our respondents often saw packaged-goods brands as interchangeable. In many instances, respondents speculated that their brand usage was more a result of habit versus loyalty. In more than any other category, respondents said they were loyal to the “brand I grew up with.”

Loyalty to packaged-goods brands hinges on having product features that resonate with the core shopper. If a brand does not deliver on the desired features or value proposition, shoppers don’t call customer service; they simply change brands.

Respondents were quick to support brands that deliver consistent quality, enhanced by unique product benefits (Baked Lays), memorable advertising (“the quicker picker upper”) and credible recommendations (dental professionals). In paper towels, much of the loyalty to Viva was driven by the benefit and value of its select-a-size feature. However, the benefit of these innovations can be fleeting, and soon replicated by a competitor.

When it comes to bringing those consumer products home, our shoppers claimed loyalty to their own reusable bags. When those weren’t on hand, the default was to the second most environmentally-friendly option, either paper or plastic, which they could either reuse or recycle.

Coffee. One product that crosses multiple categories is coffee. Our respondents saw coffee as a consumer product, a retail location and a lifestyle brand. This convergence works to build loyalty with the core consumers, sometimes to obsessive and addiction-like levels. I guess the caffeine doesn’t hurt.

Starbucks, which soared this year from 432 to 100 on the 2011 Forbes Brand Keys Loyalty Leaders List, was seen by loyalists in our survey as delivering a quality product backed by thoughtful innovations such as the Starbucks card and iPhone app, superior experience and convenience.

Dunkin Donuts, which ranked #12 on the Forbes list, was a distant second in our survey. Shoppers saw Dunkin as a superior grab-and go-option, supported by innovation in food and drink, as well as rewards that spoke to its core shopper.

In summary, when the Hub asked readers how brands or retailers earned their loyalty, their responses brought us back to product quality: a consistently great product with thoughtful features that show you understand your target shopper’s lifestyle — which means it’s a good value. This product should then be supported by superior customer service, delivered by engaged, caring employees who recognize and reward the value of their loyal customers.

Loyalty can take years to develop but only minutes to lose when we take our eyes off the product quality loyal customers have come to expect and by delivering less-than-superior customer service.

So, once again: What have you done to earn the loyalty of your core shopper? Do you understand their lifestyle, needs and wants? Are you innovating in ways that makes their life better or easier? Are you messaging in ways that focus on what’s important to them? Loyalty is a two-way street.