Figures from Origo, an eCommerce standards and services body for the financial services industry, show that 46% of single pension pots that were transferred to annuities in 2013 using the Options Transfers Service were under £20,000.
Origo said its Options Transfers Service processes about 95% of the industry's pension to annuity Open Market Options transfers.
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It serves 60 financial services brands.
The statistics, gathered to 30 December 2013, revealed that 24% of single pots transferred were under £10k, 11% were under £5k, and overall 80% were under £50k.
Currently HMRC considers £18k as a small pension pot.
Origo managing director Paul Pettitt said as auto-enrolment beds in, the number of small pension pots requiring automatic transfer will increase substantially over the next few years, particularly as opt-out rates are much lower than expected.
He said: "The fast and efficient transfer of pension pots and assets is becoming a growing issue for the pensions industry.
"While much of the DWP's attention to date has been on the sign-up process for auto enrolment, it is inevitable that the ability to transfer pensions securely, quickly and efficiently for the benefit of the consumer will become a key industry focus."
The total value of transfers since the service was launched in 2008 is over £40bn.