What if you had bought last year's worst performer on the first trading day of this year?

Experiment setup

Result

The only inputs were two closing prices from last year

The rule is a single line. Compare the first and last closing prices of 2025, then take the biggest decliner and the biggest gainer among the 30 Korean names covered here. That gave SK Innovation and SK hynix. SK Innovation went from 111,000 won to 101,200 won, down 8.83%. SK hynix went from 171,200 won to 651,000 won, up 280.26%. No earnings and no industry outlook entered the choice. Because the rule reads one scorecard and buys on the first trading day of the new year, what this experiment measures is the rule, not the companies.

Eight months later the two accounts are 10.48M won apart

At the close of 2026-01-02 SK Innovation was 99,900 won and SK hynix was 677,000 won, so 10M won bought 100.1 shares and 14.77 shares. Valued at the closes of 138,300 won and 1,647,000 won on September 4, the accounts stand at 13.84M won and 24.33M won. The loser-picking account made 3.84M won in eight months, which is not a bad outcome on its own. Over the same window, though, the KOSPI moved from 4,309.63 to 6,687.21, a gain of 55.2%, so simply holding the index would have done better. The other account more than doubled the index.

Opened at the end of June, the gap was 29.64M won

The end of June was the turning point for both accounts, in opposite directions. The SK Innovation account sat at 9.5M won that day, below its starting capital and 35.1% down from 14.63M won at the end of April. The SK hynix account was at 39.14M won, its highest reading of the eight months. Over the next two months the order held but the distance shrank. The loser account climbed from 9.5M won to 13.84M won, while the winner account fell from 39.14M won to 24.33M won, a loss of 14.82M won or 37.8% from its peak. The gap closed from 29.64M won to 10.48M won mostly because the leader gave back more than the laggard gained.

Last year's number two became this year's number 29

Following last year's winner was not a safe rule either. The second biggest gainer of 2025 was Korea Electric Power, up 141.31% from 19,560 won to 47,200 won. Bought under the same rule at 46,500 won on the first trading day of this year, it closed at 32,150 won on September 4, a loss of 30.86% and second from the bottom among the 30 names. Since picking from last year's leaderboard produced that too, what this experiment rejects is the loser-picking side. It does not adopt the winner-following side. The result belongs to one eight-month window and two stocks.

Key numbers

Last year's worst, now

13.84M won (+38.4%)

Last year's best, now

24.33M won (+143.3%)

Gap between accounts

10.48M won

KOSPI over the same period

+55.2%

Both accounts at end of June

9.5M won vs 39.14M won

Winner account from its peak

-37.8% (peak 2026-06-30)

FAQ

How were the two stocks chosen for this experiment?

Only by comparing the first and last closes of 2025. Among the 30 Korean names covered here, SK Innovation was lowest at minus 8.83% and SK hynix was highest at plus 280.26%. Earnings and industry conditions played no part in the selection.

What would the same money have become in the KOSPI index?

The KOSPI rose 55.2%, from 4,309.63 on 2026-01-02 to 6,687.21 on September 4. An account tracking the index would hold roughly 15.52M won. That is more than the 13.84M won of the loser-picking account and less than the 24.33M won of the winner-following account.

Does last year's ranking tell you anything about this year's?

In this window both directions produced a counter-example. Last year's worst grew its capital yet lagged the index, while Korea Electric Power, second best last year, fell 30.86% and finished second from the bottom. This is one eight-month window, so a different start date gives a different answer.