| ● | In the case of three months ended December 31, 2019, substantial increase in foreign currency transaction losses, primarily related to the revaluation of Indian rupee denominated intercompany note, primarily due to a substantial depreciation of the Indian rupee against the U.S. dollar and an increase in tax expense due to improved results of operations |
High repeat business and client concentration are common in our industry. During the three months ended December 31, 2019 and 2018, 96% and 88%, respectively, of our revenue was derived from clients who had been using our services for more than one year, including clients acquired from eTouch Systems Corp. in March 2018. During the nine months ended December 31, 2019 and 2018, 97% and 89%, respectively, of our revenue was derived from clients who had been using our services for more than one year, including clients acquired from eTouch Systems Corp. in March 2018. Accordingly, our global account management and service delivery teams focus on expanding client relationships and converting new engagements to long-term relationships to generate repeat revenue and expand revenue streams from existing clients. We also have a dedicated business development team focused on generating engagements with new clients to continue to expand our client base and, over time, reduce client concentration.
We derive our revenue from two types of service offerings: application outsourcing, which is recurring in nature; and consulting, including technology implementation, which is non-recurring in nature. For the three months ended December 31, 2019, our application outsourcing and consulting revenue represented 55% and 45%, respectively, of our total revenue as compared to 53% and 47%, respectively, for the three months ended December 31, 2018. For the nine months ended December 31, 2019, our application outsourcing and consulting revenue represented 56% and 44%, respectively, of our total revenue as compared to 53% and 47%, respectively, for the nine months ended December 31, 2018.
In the three months ended December 31, 2019, our North America revenue increased by 12.1%, or $27.1 million, to $251.2 million, or 75.0% of total revenue, from $224.1 million, or 71% of total revenue, in the three months ended December 31, 2018. In the nine months ended December 31, 2019, our North America revenue increased by 11.0%, or $71.9 million, to $724.0 million, or 73.7% of total revenue, from $652.1 million, or 71% of total revenue in the nine months ended December 31, 2018. The increase in North America revenue for the three and nine months ended December 31, 2019 was primarily due to the increase in revenue from clients in the C&T industry group, including customer contracts with certain existing customers acquired from third parties.
In the three months ended December 31, 2019, our European revenue decreased by 15.2%, or $9.9 million, to $55.2 million, or 16.5% of total revenue, from $65.0 million, or 21% of total revenue in the three months ended December 31, 2018. In the nine months ended December 31, 2019, our European revenue decreased by 8.8%, or $16.9 million, to $175.3 million, or 17.8% of total revenue, from $192.2 million, or 21% of total revenue in the nine months ended December 31, 2018. The decrease in European revenue for the three and nine months ended December 31, 2019 was primarily due to a decline in revenue from one of our large banking clients.
Our gross profit increased by $5.5 million to $98.7 million for the three months ended December 31, 2019, as compared to $93.2 million for the three months ended December 31, 2018. Our gross profit increased by $7.0 million to $272.9 million for the nine months ended December 31, 2019 as compared to $265.9 million in the nine months ended December 31, 2018. The increase in gross profit during the three and nine months ended December 31, 2019, as compared to the three and nine months ended December 31, 2018, was primarily due to higher revenue partially offset by higher onsite effort and subcontractor costs. As a percentage of revenue, gross margin was 29.4% and 29.6% in the three months ended December 31, 2019 and 2018, respectively. During the nine months ended December 31, 2019 and 2018, gross margin, as a percentage of revenue, was 27.8% and 28.9%, respectively. The decrease in gross margin during the three and nine months ended December 31, 2019 was primarily due to an increase in subcontractors cost, higher onsite effort, and lower utilization.
We perform our services under both time-and-materials and fixed-price contracts. Revenue from fixed-price contracts represented 43% and 40% of total revenue, and revenue from time-and-materials contracts represented 57% and 60% of total revenue for the three months ended December 31, 2019 and 2018, respectively. Revenue from fixed-price contracts represented 41% and 40% of total revenue and revenue from time-and-materials contracts represented 59% and