Philadelphia Insurance Companies (PHLY) observed its 55th anniversary in 2017. Five and a half decades may not seem like a long time compared to some companies, but it's no small feat for a company that grew out of a small insurance agency into one of the top performing insurance carriers in the country. And I promise you, we're not going to let 'middle age' slow us down.
PHLY's financial results continue to trend up, allowing us to provide reliable service to our customers. A.M. Best affirmed our "A++" rating that we've held since 2011. Gross written premiums grew last year by 3% to $3.4 billion. Our combined ratio of 93% continues to outperform the property/casualty insurance industry which averaged 103%+. We saw growth in our Surety Division, which has climbed to the 12th largest Surety Division in the country after just seven years. Valley Forge Insurance Brokerage, our in-house broker, provided much needed service to our agents and grew business by 56% from 2016. And more than 50 agents attended our inaugural, two-day Preferred Producer Training. This event for agents who are new to the insurance industry supported our key business partners by showing them how to maximize professional success and provide the best coverage for customers.
Customers gave us a 95% overall satisfaction rating. This is also backed by PHLY's Net Promoter Score (NPS) - an index ranging from - 100 to 100 that measures the willingness of customers to recommend a company's products or services to others. Our NPS has improved by nearly 20 points (50%) since 2013, and reached a new high of 68 last year. Exceeding expectations has been a focus since day one for PHLY and will continue to be part of the foundation to our success.