The average defined benefit (DB) transfer values slightly increased to £234,000 at the end of May, according to actuarial firm XPS Pensions Group (formally Xafinity).
This value is above the previous month's figure, when it stood at £232,000, according to the specialist in pensions actuarial, consulting and administration.
Over the first quarter of 2018, transfer values initially dropped, before returning to levels seen at the beginning of the year.
During 2017, transfer values remained high, but in line with the figures of the previous year - at an average of £234,000 at the end of 2016.
The difference between maximum and minimum readings of the index in May was £5,700 (or around 2.4 per cent).
The index tracks the transfer value that would be provided by an example defined benefit scheme to a member aged 64 who is currently entitled to a pension of £10,000 each year starting at age 65 and increasing each year in line with inflation.
According to Sankar Mahalingham, head of defined benefit growth at XPS Pensions Group, the increase in transfer values in May was mainly due to a fall in gilt yields during the second half of the month, with inflation remaining relatively stable.
He said: "Transfer values remain close to historic highs, but have not been very volatile, a trend that we have seen since the start of the final quarter of 2017."
Since the introduction of pension freedoms in 2015, the number of people transferring out of their defined benefit pensions has been soaring, as savers seek to take advantage of sky-high transfer values and to move their nest eggs into defined contribution (DC) schemes in order to access their cash.
According to the Office for National Statistics, funds transferred out of pension schemes almost tripled to a record £34.2bn in 2017.