Amazon Web Services (AWS) has a 45 percent share of the worldwide public cloud market, more than twice the size of the next three public IaaS providers combined, according to new data from Synergy Research Group.

The big four cloud providers – Amazon, Microsoft, IBM and Google – control well over half of the worldwide market while continuing to grow their market share. A recent report by Gartner found that IaaS revenue will grow more than 25 percent per year through 2019.

Quarterly cloud infrastructure service revenues, which include public IaaS, public PaaS, and managed private cloud, reached “well over $8 billion” and will continue to grow 50 percent per year, according to Synergy’s Q3 2016 report.

“Scale is the name of the game, especially in the public cloud markets,” John Dinsdale, a Chief Analyst and Research Director at Synergy Research Group said in a statement. “Amazon, Microsoft and Google continue to invest huge amounts in their hyperscale data center infrastructure, and all three have recently expanded their data center footprints and also announced plans to open up more geographic regions in the coming months.”

“This scale is the prime reason why they are able to gain market share and pressure smaller players into consolidation or refocusing their cloud activities,” he said. “Some tier 2 players are looking to buck the trend and at least some are seeing particularly strong growth, including Alibaba (particularly in IaaS) and Oracle (in PaaS).”

In the public PaaS market, Amazon is ahead of Salesforce, Microsoft and IBM. Big Blue is the market leader in the managed private cloud segment, followed by Amazon, Rackspace and NTT.