Who's minding your store? Who is responsible for your brand image and your reputation? Whom do your customers interact with the most?
It's my experience that in most companies it is actually the lowest paid, highest turnover employees who have the greatest impact on your customer service and your brand image. The telephone customer service rep, the hotel front desk clerk, the airline gate agent, the security guard at the hospital, the waitress.
How do they feel they are treated as employees? What do they think about your company? You can not out-perform your own self-image. And when it comes to customer service you can not out-perform your front line employee's perception of you as an employer.
Your employees will not treat the customer better than they themselves are treated.
These are the people who talk to your customers, and listen to them. They are the ones who collectively make or break your brand. Not you. Not your CMO or your ad agency. Your lowest paid employees.
And middle-management will not treat these employees better than they themselves are treated by senior-management, and so on.
This starts at the top.
Put your employees at the top of your mission statement, ahead of your customers, and show that commitment in everything you do. Make it real, not just a slogan.
Measuring what your customers think about you is a lagging indicator.
Measuring what your employees think of you. Now that's a leading indicator.