why such a discount?

I'm a bit of a newbie, and I was wondering if anyone can answer a question I have about MLT but also LICs in general.

By my calculations, MLT has been trading at an 8-9% discount to the NTA lately. However its main competitors (for my investment capitol at least), AFI and ARG have been trading with next to no discount or even a premium.

Does anyone have an explanation for this, or is it just a quirk of the market and all will be evened out over time? I would have thought that the reporting of the NTA every month would act as a "not very liquid" arbitrage mechanism. In short, why would people buy ARG at a premium to NTA while MLT is at such a discount?

Am I missing something here? Are people taking a punt on the medium term outlook of the underlying stock, in which case are these stocks forecast indicators instead of trailing indicators? Is it a liquidity issue? I notice Comsec offer a higher LVR on their margin loans for ARG and AFI than MLT, does this have any noticeable effect?

Any help would be most appreciated.