"What you don't measure, you can't improve."

These words have become the rallying cry of a world obsessed with big data and metrics. From the Fitbits strapped around our wrists to the dashboards on our Salesforce homepages, we are a generation focused on measuring success.

But all of this is nothing new for sales. It's arguable that sales has long been the poster child for measuring success. Sales managers were checking on quotas decades before marketing could tie their activity to concrete ROI.

But sales measurement has progressed along with other departments as technology continues to provide more transparency and insight in business performance. So how are some of the best salespeople measuring success today? It might not be as straightforward as you think. We rounded up five sales experts to find out.

1. Measure Sales Success by Repeat Business

“Repeat customers and referrals. If you get those you know, you’ve done a great job identifying the right clients and selling the right way."

- John Barrows, Sales Trainer

2. Measure Sales Success with a Complete Picture

"We are too fast to judge success by short-term goals and too slow to work towards building the salespeople, the sales processes, and the sales culture that enables long-term sustained growth. Like anything else, measuring one number, and excluding dozens of other factors that are also worth considering, doesn’t tell the whole story.“

- Anthony Iannarino, Author, Speaker and Entrepreneur

3. Measure Sales Success by Growth and Progress

"The notion of sales success as a fixed metric, like quota achievement, is illusory at best, as that definition of success will necessarily change from year to year. Your focus must be on growth and progress. Have you increased your individual sales capabilities or the collective capabilities of your sales team in the past year? Have you increased your product knowledge and industry expertise so that you can better serve your prospects?"

- Andy Paul, Sales Process Expert, Speaker and Author

4. Sales Success Measured by Passion

"Aside from meeting your quota, success is having your life be in honor of something. I once heard someone say ‘Most people get up in the morning because they didn’t die overnight!’ Ha! Living life as if it matters is the key to success. It includes constant learning, discovery, contribution, and challenge! Love your life UP!"

- Dianna Smith, Founder of Irreverent Sales Girl

5. Sales Success Measured by Pipeline

"The best way to measure success is to dig into the pipeline of sales opportunities. A good sales manager naturally moves from discussing results (a look at the past), directly to an evaluation of the sales pipeline (a look into the future). A healthy pipeline has three important characteristics: It’s full, it’s balanced, and it’s moving."

- Mike Weinberg, Author, Founder of The New Sales Coach

Even with the added transparency of advanced tracking and analytics, nailing down one definition of sales success continues to be allusive. If the varience in the responses of our experts is any indication, sales success is something that is defined and measured based on your company's unique goals and strategies.

How are you measuring sales success? Let us know in the comments below.