Ladies and gentlemen, thank you for standing by, and welcome to Sunlands' fourth quarter and full year 2021 earnings conference call. Today's conference call is being recorded. I would now like to turn the call over to your host today, Yuhua Ye, Sunlands' IR representative. Please go ahead.
Hello, everyone. Thank you for joining Sunlands' fourth quarter and full year 2021 earnings conference call. The company's financial and operating results were issued in our press release via Newswire services earlier today and are posted online. You can download the earnings press release and sign up for our distribution list by visiting our IR website, site. Participants on today's call will be our CEO, Mr. Tongbo Liu, and our CFO, Selena Lu Lv. Management will begin with prepared remarks, and the call will conclude with a Q&A session. Before I hand it over to the management, I'd like to remind you of Sunlands' safe harbor statement in relation to today's call. Except for the historical information contained herein, certain of the matters discussed in this conference call are forward-looking statements.
These statements are based on current trends, estimates and projections, and therefore you should not place undue reliance on them. Forward-looking statements involve inherent risks and uncertainties. A number of important factors could cause actual results to differ materially from those contained in any forward-looking statements. For more information about potential risks and uncertainties, please refer to the company's filings with the Securities and Exchange Commission. With that, I will now turn the call over to our CEO, Tongbo Liu.
Thank you, Yuhua. Hello, everyone. Welcome to Sunlands' fourth quarter and full year 2021 conference call. The year 2021 was full of uncertainties on both the macro and education industry levels. Given the challenges, we strengthened our focus on healthy, steady growth to overcome obstacles and prepare to capture opportunities ahead of us. More specifically, we strove to streamline our operations with a leaner organization and disciplined cost control measures, continue to optimize our product mix to concentrate on demand-driven markets, and spend efforts on improving services and acquiring students in a more efficient manner.
As a result of our clear strategic plan and steadfast execution, we are delighted to close 2021 with record high net profits of CNY 115.8 million in the fourth quarter, and CNY 212.4 million for the full year, delivering on our commitment to balanced growth and profitability. Our improved profitability amidst the year-over-year moderation in course billings and new student enrollments well reflects the effectiveness of our strategic direction and execution excellence. Now, let's turn to the performance of each of our major course programs. In terms of professional certification and skills programs, we believe there is still huge market potential on the demand side.
On one hand, we have demand from working professionals who not only seek to stay competitive through job relevant or credential courses, but also increasingly take courses to complement their primary skills and develop new interests and hobbies. On the other hand, these programs are also attracting students from a wide range of age groups who are looking for interest-based learning as part of a new lifestyle. To tap this potential, we continue to focus on developing a diverse range of courses to fulfill the ongoing interest or robust learning demand during the first quarter. Thanks to our expansive course resources, our net revenues and gross billings for professional certification and skills programs in the quarter increased by 13.5% and 16.5% year- over- year, respectively.
Going forward, we will continue to diversify our course catalogs and tailor our courses to a greater variety of learner groups. As the breadth and depth of our course offerings expand, we believe our professional certification and skills programs will capture the increasing share of the market and realize continued growth. With respect to our post-secondary courses, as we strove to fine-tune our product portfolios, we strategically shifted our focus toward master's degree -only programs to capitalize on growing demand. Most of our students for these programs are working professionals. As the jobs market becomes more competitive due to ongoing pandemic-related challenges, an increasing number of working age people are realizing the importance of postgraduate education.
China's 2022 national postgraduate entrance exams received another record-setting number of applicants, jumping by 21.2% year-over-year to 4.6 million, while admission became increasingly difficult, as reflected by an approximately 9% year-over-year decrease in 2021's acceptance rate. Pressure mounting on their career paths and competition for postgraduate education is intensifying, more applicants are turning to us to utilize our professional preparation courses to improve their odds of acceptance and thereby and thereby enhance their competitiveness at work, driving increased demand of master's degree-oriented programs. Riding this tailwind, net revenue from our master's degree-oriented programs grew 5.5% and 13.6% year-over-year for the first quarter and the full year respectively.
New course billings and the new student enrollments for the segment also continued their upward trend in full year 2021, despite a year-over-year decline in the fourth quarter due to the step up of our balanced growth and profitability strategy. In 2022, we will continue to leverage our highly capable teams experienced in MBA exam preparation to solidify our leadership position by expanding our course portfolio and optimizing our teaching and the service. Regarding our STE programs, we remain committed to enriching our course offering, improving operating efficiency and the service quality during the quarter. Given our established effective teaching system and the results-driven teaching methods, we continue to deliver high teaching quality and provide the premium courses to our students.
Meanwhile, we took further measures to control spending and enhance our student acquisition efficiency, which in turn has driven high quality growth. Thanks to our effective cost control measures, our cost structure improved during the first quarter, with sales and marketing expenses and general and administrative expenses down 14.2% and 7.6% year-over-year respectively. However, we continue to pump new blood into our growth strategy by maintaining our investment in new course development, as evidenced by a slight increase in product development expenses of 0.5% year-over-year in the fourth quarter. Furthermore, we remain focused on improving student acquisition efficiency by adopting more cost-effective acquisition channels and leveraging course -selling opportunities while customizing sales and marketing solutions for different students group based on their unique profile and needs.
We are pleased to see our strategy already bearing fruit over the past three quarters and for the full year 2021. With a successful turnaround in profitability, Sunlands demonstrated both its resilience and agility when navigating challenges amid 2021's shifting industry landscape. In 2022 and beyond, we will continue to align our business operations with our strategic objectives to bring value to our students, employees, shareholders, and the broader society. With that, I will turn the call to our CFO, Selena, to run through our financials.
Thank you, Tongbo. Hello, everyone. We are excited to register net income of CNY 150.8 million in the fourth quarter, compared to the net loss of CNY 73.5 million for the same period last year, marking our third consecutive quarter of profitability. This solid performance was driven by our 0.7% year-over-year top line growth and a 40.5% year-over-year decline in operating expenses due to our strengthened expense management practices. Our net profit margin expanded significantly to 25.6% in the fourth quarter, up 38.2 percentage points year-over-year and 10 percentage points quarter-over-quarter.
Looking ahead, we are steadfast in our commitment to offering premium course content and services to our students while adopting effective measures to further reduce costs and boosting operating efficiency, aiming to achieve long-term sustainable growth. Now, let me walk you through some of our key financial results for the fourth quarter 2021. All comparisons are year-over-year, and all numbers are in RMB unless otherwise noted. In the fourth quarter, our net revenue was CNY 588.9 million, an increase of 0.7% year-over-year. Cost of revenue decreased by 8.6% to CNY 89.4 million in the fourth quarter from CNY 97.8 million in the fourth quarter of 2020. The decrease was primarily due to, number one, declined compensation expenses related to our cost of revenues personnel.
Number two, reduced insurance related costs incurred for our integrated online education service package purchased by students. Gross profit increased by 2.6% to CNY 499.5 million from CNY 486.7 million in the fourth quarter of 2020. In the fourth quarter, operating expenses were CNY 400.5 million, representing a 40.5% decrease from CNY 673.7 million in the fourth quarter of 2020. Sales and marketing expenses decreased by 44.2% to CNY 339.4 million in the fourth quarter from CNY 608.5 million in the fourth quarter of 2020. The decrease was mainly due to lower spending on branding and marketing activities and the declined compensation expenses related to our sales and marketing personnel.
General and administrative expenses were CNY 50.5 million in the fourth quarter of 2021, decreased by 7.6% year-over-year, mainly due to a decrease in rental expenses and a decline in compensation expenses related to general and administrative personnel. Product development expenses increased by 0.5% to CNY 10.7 million in the fourth quarter from CNY 10.6 million in the fourth quarter of 2020. Product development expenses were mainly comprised of compensation expenses. Other expenses were CNY 3.1 million in the fourth quarter, compared with other income of CNY 109.4 million in the fourth quarter of 2020. The decrease was primarily because of the value-added tax exemption offered by the relevant authorities as part of the national COVID-19 relief effort, came to an end in April 2021.
Net income for the fourth quarter was CNY 150.8 million, compared with net loss of CNY 73.5 million in the fourth quarter of 2020. Basic and diluted net income per share was CNY 22.89 in the fourth quarter of 2021. As of December 31st, 2021, the company had CNY 676.7 million of cash equivalents, and restricted cash, and CNY 184.2 million of short-term investments. As of December 31, 2021, the company had a deferred revenue balance of CNY 2,348.2 million, compared with CNY 3,024.4 million as of December 31st, 2020. Capital expenditures were incurred primarily in connection with IT infrastructure equipment and the leasehold improvement necessary to support the company's operations.
Capital expenditures were CNY 5.2 million in the fourth quarter, compared with CNY 4.7 million in the fourth quarter of 2020. For more of our 2021 full year financial results, please refer to our earnings press release for further details. Now for our outlook. For the first quarter of 2022, Sunlands currently expects net revenues to be between CNY 590 million-CNY 610 million, which would represent a decrease of 15% to 12.1% year-over-year. This outlook is based on the current market conditions and reflects the company's management's current and preliminary estimate of market operating conditions and the customer demand, which are all subject to change. With that, I'd like to open up to the call to the questions. Operator?
Thank you. We will now begin the question and answer session. To ask a question, you may press star then one on your touch-tone phone. If you are using a speaker phone, we ask that you please pick up your handset before pressing the keys. To withdraw your question, please press star then two. For the benefit of all participants on today's call, if you wish to ask your question to management in Chinese, please immediately repeat your question in English. Ladies and gentlemen, as a reminder, if you would like to ask a question, please press star and one at this time. Showing no further questions, this will conclude our question and answer session. At this time, I'd like to turn the conference back over to Yuhua Ye, IR Representative, for any closing remarks. Yuhua, the line is open for your closing remarks.
Once again, thank you everyone for joining today's call. We look forward to being with you again soon. Good day and good night.
Thank you. This concludes the earnings conference call. You may now disconnect your lines and have a wonderful day.