In the three months ended September 30, 2022, we served 23,816 unique product developers and engineers who purchased our products through our web client, up 1.5% over the same period in 2021. In the nine months ended September 30, 2022, we served 47,793 unique developers and engineers who purchased our products through our web client, up 2.4% over the same period in 2021.
Operating expenses include marketing and sales, research and development, and general and administrative expenses. Personnel costs are the most important component of each category.
Revenue and related changes by reportable segments for the three months ended September 30, 2022 and 2021 are as follows:
Revenue and related changes for the three months ended September 30, 2022 and 2021 are as follows:
Changes in the fair value of the contingent consideration. We have no contingent liability for refunds registered in 2022. For the three months ended September 30, 2021, the change in the fair value of the contingent consideration associated with the acquisition of Hubs was $0.8 million.
Revenue and related changes by reportable segments for the nine months ended September 30, 2022 and September 2021 are as follows:
Revenue and related product line changes for the nine months ended September 30, 2022 and September 2021 are as follows:
Changes in the fair value of the contingent consideration. We have no contingent liability for refunds registered in 2022. For the nine months ended September 30, 2021, the change in the fair value of the contingent consideration associated with the acquisition of Hubs was $8.5 million.
The table below shows our cash flows for the nine months ended September 30, 2022 and September 2021:
Please refer to note 2 to the consolidated financial statements set out in paragraph 1 of Part I of this quarterly report on Form 10-Q for information on recent accounting announcements.