More than two thirds of investment companies (excluding VCTs) now have discount control mechanisms (DCMs) in place, compared to about 40% five years ago, but some industry commentators believe further action should be taken as no trust should be "sitting on a discount of 10% for more than a year".
DCMs have become increasingly popular with boards in recent years, and contributed to average discounts reaching historically narrow levels in Q1 of 5%.
The AIC's figures include those trusts which can implement hard mechanisms such as zero discount policies, as well as redemption options and the ability to buy back shares.
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However, some investors, like Mark Dwyer of City of London Investment Management Company, think all trusts should have an effective DCM in place to enhance shareholder value.
The group, which manages $4.5bn, invests in closed-ended funds in both the UK and US using a value approach.
Dwyer, CIO EM CEF Group, said it is unacceptable if an investment trust trades on a discount of 10% or wider for more than a year and DCMs are "an integral part of avoiding that".
He commented: "If boards leave discounts to languish, investors will shy away from trusts. But the industry needs to be large enough to meet the needs of both retail and institutional investors and that cannot happen if discounts are left unchecked.
"The industry cannot grow unless existing trusts can issue new shares, which cannot be done when they are trading on a discount."
But Ewan Lovett-Turner, director of investment companies research at Numis Securities, said while there is a place for DCMs, it is about having the appropriate policy in place.
He said: "At a fundamental level, a DCM is only tapping one side of the equation. It does not stimulate new demand and for a trust to trade at a premium and trade well, you need the support of buyers, good performance and marketing.
"A trust also needs to be in a position of strength before adopting a DCM. If it is already small with a limited performance record, the options are restricted.
"Instead, those types of funds should be assessing whether or not their mandate is still relevant."
However, Lovett-Turner praised the investment trust sector for becoming "savvier" in controlling discounts, compared to the period before the 2008 financial crisis.
"A lot of mandates back then were not really relevant or had long management contracts with no exits or discount controls so investors were scuppered," he added.
"There has now been a big effort to make sure new products have some visibility of liquidity at some point in the future."
