Microsoft’s Azure public cloud business is certainly growing. What’s not certain is exactly how big it is. An analyst at J.P. Morgan has taken a guess, as the Wall Street Journal reported today.

If the analyst is right, Azure pulled in around $2.7 billion in revenue in all of 2016. Put another way, for each quarter in 2016 Azure brought in, on average, $675 million in revenue. J.P. Morgan didn’t respond to a request for comment. Neither did Microsoft.

Assuming the estimate is correct, it would mean Azure is around 22 percent the size of public cloud market leader Amazon Web Services. Amazon’s AWS business captured $12.2 billion in revenue for the entire year.

Azure is thought to be second only to AWS in the cloud infrastructure market. Meanwhile, the Google Cloud Platform, thought to be No. 3 in the business, pulled in more than $1 billion in revenue in 2017, Raymond James analyst Aaron Kessler estimated, according to the Journal.

Microsoft has declined to disclose actual revenue numbers for Azure since introducing it in 2008, two years after Amazon launched AWS. What Microsoft does talk about these days is Azure revenue growth rates. For example, in the fourth quarter of 2016 Azure revenue rose 93 percent year over year. By comparison, in that period AWS revenue in Q4 was up 47 percent, and in the previous quarter, Azure revenue had been up 116 percent.

Microsoft also said Azure’s compute usage more than doubled year to year in the fourth quarter. AWS does not generally disclose numbers about compute usage.

Microsoft has done many things to ensure Azure is an attractive place for developers to run workloads. Among other things, Microsoft refreshed some of its virtual machine (VM) instances, cut the prices of certain instances, began a preview of instances backed by graphics processing units (GPUs), opened new data center regions, and unveiled a tool for running chatbots.