the sale of 3D printers. In 2022, we recognized an increase in the reserve for slow-moving inventory amounting to kEUR 946 negative, compared to kEUR 851 negative in 2021.
Gross profit for our Services segment increased to kEUR4,254 for the year ended December 31, 2022 from kEUR 2,699 in the same period of 2021. The gross profit margin for this segment increased to 35.4% for the year ended December 31, 2022 from 29.7% for the same period in 2021. Those increases in gross profit as well as gross profit margin were mainly related to significantly higher contributions from our German operation as well as our subsidiary voxeljet America, as a result of the improved utilization of those service centers. Both service centers were able to generate considerably higher revenues in 2022 compared to last year, therefore, the utilization was very cost efficient. This was partially offset by weaker gross profit and gross profit margin contributions from our Chinese service center.
Selling expenses were kEUR 7,975 for the year ended December 31, 2022 compared to kEUR 6,420 in the same period in 2021, representing a significant increase of kEUR1,555, or 24.2%. This was mainly due to higher distribution expenses primarily corresponding to the increase in revenues. Shipping and packaging expenses as a main driver of the selling expenses could vary from quarter to quarter depending on quantity and types of products, as well as the destinations where those goods are being delivered.
Administrative expenses slightly increased by kEUR7 to kEUR 6,584 for the year ended December 31, 2022 from kEUR 6,577 in the prior year period and were therefore almost flat.
Research and development expenses increased to kEUR 6,865 for the year ended December 31, 2022 from kEUR 6,149 in the same period in 2021, a increase of kEUR716, or 11.6%. This was mainly due to higher material expenses as well as higher usage of external services in 2022 compared to last year’s same period 2021.
Other operating expenses for the year ended December 31, 2022 were kEUR 2,591 compared to kEUR 618 in the prior year period. This is mainly due to higher losses from foreign currency translations. Foreign currency losses amounted to kEUR 2,339 for the year ended December 31, 2022, compared to kEUR 460 in the same period in 2021.
Other operating income was kEUR 10,447 for the year ended December 31, 2022 compared to kEUR 2,970 in the prior year period. The increase was mainly due to the gain from the sale and leaseback transaction amounted to kEUR 4,335. In addition, we recorded higher gains from foreign currency transactions amounting to kEUR 2,634 in 2022 compared to kEUR 1,812 in 2021. Furthermore, the reclassification of the foreign currency translation reserve, which was previously recognized in other comprehensive income on consolidation of voxeljet UK accounts, to profit and loss accounts on deconsolidation resulted in an other operating income of kEUR 1,475, related to the finalization of the wind-up on February 17, 2022. Additionally, other operating income for the year ended December 2022 included kEUR 597 in reimbursement of research and development costs, compared to kEUR 110 in the comparative period. Moreover, other operating income included kEUR 877 from the receipt of government grants awarded for research and development project funding for the year ended December 31, 2022 compared to kEUR 617 for the year ended December 31, 2021.
The changes in foreign currency losses and gains were primarily driven by the valuation of the intercompany loans granted by the parent company to our US subsidiary.
Operating loss was kEUR 5,382 for the year ended December 31, 2022, compared to an operating loss of kEUR 8,844 in the comparative period in 2021. This was mainly due to a positive net impact of the year over year changes in other operating expenses and other operating income amounting to kEUR 5,504, mainly related to the gain from the sale and leaseback transaction with IntReal International Real Estate Kapitalverwaltungsgesellschaft mbH closed on October 31, 2022, the reclassification of the foreign currency translation reserve to profit and loss accounts on deconsolidation of voxeljet UK accounts and the impact from the foreign currency transactions as mentioned above. In addition, gross profit for 2022 increased by kEUR 236 compared to last year. This was partially offset by higher selling expenses as well as higher research and development expenses with increases of kEUR 1,555 and kEUR 716, respectively. Administrative expenses were almost flat.
Financial result was negative kEUR 6,129 for the year ended December 31, 2022, compared to negative kEUR 1,677 in the comparative period in 2021. This was mainly due to the write-down of bifurcated embedded derivative financial asset