due to increased transaction volume as well as higher compensation costs associated with additional personnel to support growth in active locations. Professional Services and Other Total professional services and other cost of revenue increased $0.9 million , or 21.3% , to $5.3 million for the year ended December 31, 2021 from $4.3 million for the year ended December 31, 2020 . This increase was primarily the result of increased consulting costs and higher compensation costs to support growth in active locations. Gross Profit Gross profit margin decreased to 79.4% for the year ended December 31, 2021 from 81.0% for the year ended December 31, 2020 . Decreases in gross profit margin were driven by higher platform and professional services and other compensation costs to support rapid growth in transactions and active locations coming onto the platform. Operating Expenses Research and Development Year Ended December 31, Change 2021 2020 $ % (in thousands, except percentages) Research and development $ 58,918 $ 32,907 $ 26,011 79.0 % Percentage of total revenue 39.4 % 33.4 % Research and development expense increased $26.0 million , or 79.0% , to $58.9 million for the year ended December 31, 2021 from $32.9 million for the year ended December 31, 2020 . This increase was primarily the result of higher compensation costs associated with additional personnel and an increase in the use of software tools to support further investments in our platform development and continued product innovation. Additionally, we incurred a non-cash charge of $1.8 million in March 2021 related to the vesting and settlement of stock appreciation rights, or SARs, in connection with the IPO . We also incurred $0.4 million in transaction costs related to the Wisely Acquisition that closed on November 4, 2021. As a percentage of total revenue, research and development expenses increased to 39.4% for the year ended December 31, 2021 from 33.4% for the year ended December 31, 2020 . General and Administrative Year Ended December 31, Change 2021 2020 $ % (in thousands, except percentages) General and administrative $ 69,625 $ 22,209 $ 47,416 213.5 % Percentage of total revenue 46.6 % 22.6 % General and administrative expense increased $47.4 million , or 213.5% , to $69.6 million for the year ended December 31, 2021 from $22.2 million for the year ended December 31, 2020 . This increase was primarily a result of increased compensation costs due to increased headcount to support the growth and stage of the organization , IPO related bonus awards, vesting and settlement of SARs in connection with the IPO, as well as increased insurance costs and professional fees incurred in preparation for becoming and operating as a public company. We also incurred a non-cash charge of $13.1 million for the year ended December 31, 2021 related to the donation of 345,836 shares of our Class A common stock to a charitable donor- advised fund. We expect to donate additional shares in the future to this fund in conjunction with our Olo for Good initiative . Additionally, we incurred $1.9 million in transaction costs related to the Wisely Acquisition that closed on November 4, 2021. As a percentage of total revenue, general and administrative expenses increased to 46.6% for the year ended December 31, 2021 from 22.6% for the year ended December 31, 2020 . 59