(Bloomberg) -- Microsoft Corp. generates most of its artificial intelligence revenue from OpenAI, according to new disclosures from the company. Microsoft didn't update the total AI sales figure when it reported fiscal fourth-quarter earnings last week. The disclosure suggests that OpenAI accounted for more than half, and likely about 70%, of Microsoft's actual AI sales during its most recent fiscal year — highlighting how dependent Microsoft remains on its close partner. But investors charting Microsoft's progress in AI have continued to question how much of its revenue is generated by OpenAI. Bloomberg's analysis assumes that Microsoft's annual AI run rate continued growing at the rapid 123% the company reported for March.