Avoid Overpaying ETFs Using Premiums and iNAV

TL;DR

• Premium (discount) measures the percentage gap between an ETF market price and the underlying net asset value (NAV).
• iNAV is an intraday NAV estimate, useful for checking excessive premiums or discounts relative to real-time prices.

Definition of Premium (Discount)

The premium (discount) is commonly calculated as follows.

Premium(%) = (ETF market price - reference NAV) / reference NAV × 100

The reference NAV is usually the prior close NAV or the NAV reported after market close. A positive number is called a premium, a negative number a discount.

What is iNAV and why it matters

iNAV (intraday NAV) is an intraday estimate of NAV that reflects real-time prices of the underlying assets. Because ETFs trade intraday, market prices often diverge from the prior NAV. Checking iNAV lets you quickly see where the market price stands relative to the actual asset value.

Benefits of iNAV

• Assess intraday premium: Comparing the market price to iNAV rather than prior NAV gives a more accurate read on whether the price is excessively high or low.
• Support liquidity assessment: Viewing iNAV together with bid-ask spreads and trading volume helps reduce execution risk.

Common misunderstandings

1) "Premium of 0 means perfectly fair price," even when premium is 0, execution costs such as bid-ask spread, brokerage fees, and taxes are separate.
2) "iNAV is absolutely accurate," iNAV is an estimate and can be off due to delayed quotes or trading halts in the underlying assets.
3) "Small premium always means safety," judging only by a single premium snapshot can still lead to losses during liquidity shocks.

Calculation example (hypothetical numbers)

For illustration:

• Prior close NAV: 10,000 KRW
• Intraday iNAV (real-time estimate): 10,200 KRW
• Current ETF market price (ask): 10,500 KRW

Premium (prior NAV basis) = (10,500 - 10,000) / 10,000 × 100 = 5.0%

Premium vs iNAV = (10,500 - 10,200) / 10,200 × 100 ≈ 2.94%

Interpretation: Compared with prior NAV it is a 5% premium, but compared with intraday iNAV it is about a 2.9% premium. Relying only on prior NAV can understate or overstate the true extent of overvaluation.

(Table) Summary comparison

Practical checklist

• Check whether iNAV is provided and how frequently it updates: confirm how often brokers or exchanges refresh iNAV.
• Bid-ask spread and execution probability: if spreads are wide or execution failures are common, factor in execution costs.
• Underlying composition and time-zone differences: overseas ETFs can see premiums due to time-zone gaps between the underlying market and the Korean market.
• Understand creation-redemption mechanics by institutions: smooth creation and redemption typically resolve premiums quickly.

Also, plotting price versus iNAV on a chart makes it easier to spot when divergences occur. See Chart Technicals for reference.

Finally, premium and iNAV are useful tools to avoid excessive premiums but are not standalone trading signals. Always synthesize multiple indicators and liquidity conditions before deciding.

This article is for informational purposes and is not investment advice.