Public cloud computing revenues are set to reach $20 billion (£12.7bn) by the end of 2016, according to an analyst report.

The report from Market Monitor, part of 451 Research, forecasts that spending on public cloud services across infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS) will increase by a compound annual growth rate of 36 percent between 2012 and 2016.

The 'Cloud as-a-Service overview' report, which forecasts the level of revenue generated by 309 cloud-services providers and technology vendors, shows that IaaS accounted for the majority of cloud market revenues in 2012, with more than half of the public cloud spend. Analysts projected a CAGR of 37 percent through to 2016 for the IaaS market.

PaaS accounted for 24 percent of the total spend in 2012, with a forecast CAGR of 41 percent, making it the fastest growing segment.

Meanwhile the infrastructure SaaS segment, which does not include enterprise SaaS revenue, accounted for 25 percent of cloud revenues and is expected to generate a 29% CAGR through 2016.

Despite the growth in spending on public cloud Yulitza Peraza, Analyst, Quantitative Services, 451 Research commented that cloud vendors still face a challenge in convincing customers that they should migrate more workloads.

"Cloud computing is on the upswing and demand for public cloud services remains strong," said Peraza.

"However, public cloud adoption continues to face hurdles including security concerns, transparency and trust issues, workload readiness and internal non-IT-related organisational issues."

The research showed that the majority of cloud vendors were making relatively small revenues from selling public cloud services, under the $5 million (£3.2m) mark.

Only 12 vendors were found to be making over $75 million (£48m) each in revenues during 2012.

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