Thank you, Yingying. Hello, everyone. Welcome to Sunlands' first earnings conference call as a public company. I'm delighted to say that our performance in the first quarter was very solid. Before our IPO, we were very clear that we see huge potential in the adult education market, and we have always believed that the online education model would drive the consolidation of this huge, fast-growing and fragmented market. We have positioned ourselves better than anyone else to benefit from it. I think our results in the first quarter really back this up. Our aggressive investments in improving the quality of our courses, in our IT platforms and in reaching up the potential markets drove record numbers of students to our platform, generating triple-digit growth in several of our key metrics.
Net revenue increased by 161%, net gross billings were up 126% and new student enrollments more than doubled compared to the first quarter last year. Besides these financial numbers, I would like to spend some time talking about a few operational numbers, which indicate some of the drivers behind this high growth rate.
First of all, let's look at the back end of our business, which mainly covers the teaching and learning process. According to iResearch, the national average pass rate of STE exam-takers, who had participated in STE tutoring courses, was only 46.5% in 2016. And our student pass rate in Jiangsu Province in 2016 was 71.9%, significantly higher than the national average. In the first half of this year, this number jumped to 79.2%. This increase was due to our focus on teaching philosophy, which boils down to a formula, teaching quality equals teaching time, times teaching efficiency. I can give you 2 numbers to back this up. The first number is the number of quizzes taken per student, which reached 970 in the first quarter this year, nearly triple the number in first quarter last year. The other number is the student satisfaction rate of our teachers, which reached around 98%.
Secondly, let's discuss the front end of our business, which mainly consists of sales and marketing activities. Our marketing effectiveness ratio, which is calculated by dividing our marketing spending by our gross billings, remained around 19% compared to 22% in the first quarter of 2017. Considering the fact that in the educational -- in education industry, students are more likely to enroll after Chinese New Year and that we had a late Chinese New Year in 2018, otherwise this percentage can be even lower.
Last, but not least, our net cash flow from operations reached RMB 222 million (sic) [ RMB 226 million ] in the first quarter this year. And our deferred revenue reached RMB 2.6 billion, which both demonstrate that we have significant capital to invest in our future strategy.
Looking forward to achieve our goal, we will focus on the following 3 areas. First of all, we will continue to recap the market to attract more students who need a bachelor's degree. According to iResearch, in China, there are more than 600 million people between ages of 18 to 48, who do not have a bachelor's degree as of December 31, 2017. And the limited capacity of the traditional higher education sector offered by the government can only meet the needs of only 20% of the people at age 18. We aim to recapitulate people by telling them that through the government-run Self-Taught Higher Examinations, otherwise known as STE, they can get a bachelor's degree and they can take it online. More precisely, we will make them aware that even with just a mobile phone, they cannot only get a higher degree but also get a higher salary and improve themselves. As more people learn about the STE system, the online STE tutoring market is expected to grow to RMB 44.7 billion in 2017. In the second quarter, we will set up new trial classes and upgrade sales and marketing methods to attract more and more customers to STE programs.
Secondly, we will continue to invest in the quality of our courses and content. The massive data collected from our student base allows us to analyze their behaviors, preferences and learning outcomes among other things. This, in turn, enables us to continuously optimize our educational content, teaching quality and the overall student experience. For example, with the help of our IT platform, our teachers were able to estimate relatively accurate number of knowledge points in the STE examinations that were held in April, just 1 month ago. And this helped our students focus their learning and improve their average pass rate. In addition, we're also improving the quality and the compensation for our teachers.
Lastly, we will keep investing in our IT platform. At the end of last year, we had nearly 600 IT employees, and by the end of this year, this number is expected to double. Our IT team focuses on both the customer side and the operations side of our business to improve our customers' learning experience and the company's efficiency at the same time. Our IT platform, Genesis, is fully integrated into every aspect of our business and provides a seamless experience to our students, and the algorithm behind this is one of the main reasons we were able to achieve such a high pass rate.
Sunlands remains a clear #1 player in the STE market. We are bigger than the #2 and #3 players combined, and we believe that as long as we continuously invest in these 3 areas, our first-mover advantages and barriers to entry will become stronger.
With that, I will hand over the call to our CFO, Steven, to run through our financials.