The Big Mac index for South Korea rose to 4.0, up from 3.47 early this year, according to data released by The Economist on Tuesday.

The index for South Korea was the 28th highest among 57 countries, based on the July 23 exchange rate of 1,023 won against the U.S. greenback. The Big Mac index, introduced by The Economist in 1986, evaluates exchange rates by comparing the prices of Big Macs in different countries.

The higher the index for a country, the less undervalued its currency is against the U.S dollar, the data said. Meanwhile, Norway, Switzerland and Venezuela posted the highest Big Mac indexes of 7.76, 6.83 and 6.82.