should not be considered representations that any such amounts have been, could have been or could be converted at that or any other exchange rate.
The increase in revenue from our Top Client in the six months ended June 30, 2021 resulted from (i) the positive effect derived from the appreciation of the Brazilian real against the U.S. dollar on our U.S. dollar-denominated revenue, and (ii) our ability to maintain close relationships with our major clients, which is essential to the constant growth and profitability of our business.
The volume of work we perform for each client may vary from year to year, and as a result, a major client in one year may not provide the same level of Net revenue for us in any subsequent year. The technology services we provide to our clients, and the Net revenue associated with those services may decline or vary as the type and quantity of technology services we provide changes over time.
Costs of services provided
Cost of services provided for the six months ended June 30, 2021 was R$394,140 thousand, an increase of R$109,883 thousand, or 39%, from R$284,257 thousand for the six months ended June 30, 2020.
This increase was due to an increase in employee expenses classified as costs of services provided, which was R$359,336 thousand for the six months ended June 30, 2021, an increase of R$110,029 thousand or a 44% from R$249,308 thousand for the six months ended June 30, 2020. The increase in employee expenses was due to promotions and new hires related to the strategic growth of our international teams in Canada, China, United Kingdom and Portugal, as we hired more employees in response to the growing demand for our services.
Gross profit
As a result of the foregoing, Gross profit for the six months ended June 30, 2021 was R$217,476 thousand, an increase of R$53,479 thousand, or 33%, from R$163,997 thousand for the six months ended June 30, 2020.
Operating expenses, net
Operating expenses increased by R$27,565 thousand, or 44%, to R$90,795 thousand for the six months ended June 30, 2021, from R$63,230 thousand for the six months ended June 30, 2020, mainly due to the variations in selling, general and administrative expenses, research and technological innovation expenses.
Selling, general and administrative expenses increased by R$29,292 thousand, or 47%, to R$91,834 thousand for the six months ended June 30, 2021, from R$62,542 thousand for the six months ended June 30, 2020. This increase was motivated by two drivers: (i) an increase in employee expenses of R$19,196 thousand or 43%, to R$63,627 thousand for the six months ended June 30, 2021, from R$44,430 thousand for the six months ended June 30, 2020, due to new hires and promotions for back-office and sales teams, and (ii) an increase in advertising and publicity expenses of R$4,939 thousand or 1,112%, to R$5,383 thousand for the six months ended June 30, 2021, from R$444 thousand for the six months ended June 30, 2020, related to the launch of a global marketing campaign in the second half of 2020.
Research and technological innovation expenses decreased by R$1,958 thousand, or 100%, to R$4 thousand for the six months ended June 30, 2021, from R$1,962 thousand for the six months ended June 30, 2020 as these expenses were related to investments in products that we discontinued, one of which resulted in the spin-off of the subsidiary CI&T IOT in the six month ended June 30, 2021.
Operating profit before financial income
As a result of the foregoing, operating profit before financial income for the six months ended June 30, 2021 was R$126,681 thousand, an increase of R$25,914 thousand, or 26%, from R$100,767 thousand for the six months ended June 30, 2020.
Net finance costs
Net finance costs decreased by R$8,466 thousand, or 70%, to R$3,686 thousand for the six months ended June 30, 2021 from R$12,152 thousand for the six months ended June 30, 2020 due to the depreciation of the U.S. dollar against Brazilian reais in the first half of 2021.