How Jupick selects its major stocks: more rules for exclusion than for inclusion

With any list, laying out the names is the easy part. The hard part is what was left out, and that usually decides the character of the list. More than 2,000 stocks are listed in Korea. Jupick's Korean screen shows only 200 of them. Without explaining where the other 1,800 went, these 200 are just names someone lined up.

No person is involved in selecting stocks at Jupick. Each day, whenever data arrives, code redraws the list from scratch. A stock on yesterday's list can drop off today, and the reverse can happen too, but each time it is not someone's judgment; the rules below simply run again.

So this article is not about which stocks were chosen because they are good. It is about the order in which a machine filtered them, and knowing that order saves a lot of wandering when looking for a stock that is not on the list.

First, only stocks listed on KOSPI, Korea's main market, and KOSDAQ, Korea's second, growth-oriented market, are considered. Second, of those, the top 200 by market cap are kept. That is all there is to the inclusion rules.

There is a reason for using market cap as the criterion. Basing it on values that swing widely from day to day, such as trading value or price gains, would turn the list over every day. A screen where the stock seen yesterday disappears today makes comparison impossible. Market cap moves with the share price, but the rankings do not reshuffle much in a single day, so it keeps the list stable while still reflecting changes in the market.

The number 200 itself has no special basis. The Korean 200 plus the overseas 200 make 400, a scale that can all be fetched fresh once a day while staying within the free limits. That the size of the list comes from the cost of fetching data is a fact with no reason to hide.

Sometimes shares of the same company are listed under two or more different stock codes, commonly called common and preferred shares. They differ in voting rights and dividend terms and their prices move separately, but they share a single set of financial statements. Putting both on the list would show the same company's same numbers on two rows and put one company into the top 200 by market cap twice.

So only common shares are kept. Korean stock codes are six characters long, and common shares end in 0. Older-style preferred shares end in 5, 7 or 9, and new-style preferred shares end in K or L, as in 00680K, 03473K and 0220WL. A single final character separates common from preferred shares.

For a while this article said something different. It stated that codes containing letters are new-style preferred shares, so one also had to check whether all six characters were digits. That was wrong, and Jupick's code was written on the same premise. Korea Exchange (KRX) also assigns codes containing letters to recently listed common shares. Samsung Epis Holdings, with the code 0126Z0, is one such case. The letter in the middle is not a preferred share marker; it is a character added to create more codes after the six positions had all been used up.

That condition was removed on August 29, 2026. Until then, 26 common shares with letters in their codes had been left off the list regardless of market cap, and one of them, with a market cap in the KRW 9 trillion range, ranked 75th overall and should have been in the top 200. The other 25 were outside the top 200, so the result was the same. Either way, this is what happens when a rule is older than the data.

Stocks whose Korean name includes the word SPAC are excluded regardless of market cap. A SPAC, or special purpose acquisition company, is a shell listed before it has found a company to acquire. Its entire business is to hold the money raised in its offering in trust and look for a merger target.

Jupick grades come from nine financial metrics. Operating margin requires sales, ROE requires earnings, and dividend metrics require an entity that distributes earnings. A SPAC has no business, so almost none of the nine can be calculated meaningfully. Attaching a grade to such a stock would disguise the absence of numbers as a grade.

The exclusion works by checking whether the name contains the word SPAC. It is not a precise test. A stock not named that way can slip through this net. Jupick considers it better to note that it uses an imperfect rule than to pretend the rule is perfect.

Besides KOSPI and KOSDAQ, Korea has one more market called KONEX. Jupick does not look at KONEX at all. It is made up mostly of early-stage small and medium-sized companies, trading is sparse, and stocks that see not a single trade all day are common. The price change for such a stock compares a price from several days ago with today's, so the phrase “change from the previous day” does not hold.

There is one handling in the other direction too. Within KOSDAQ there is a separate tier called KOSDAQ Global. It is a segment grouping blue-chip companies that meet its requirements, and in the data its market name is written differently from KOSDAQ. Jupick includes these stocks in the list but labels them KOSDAQ on screen.

This choice leans toward hiding information. The market filter on screen has only two options, KOSPI and KOSDAQ, so a third name would create stocks that match neither filter. Folding the labels into one comes at the cost of losing the segment distinction, and the decision can be reversed by adding a filter.

If the stocks that pass all the rules fall well short of 200, Jupick does not proceed with what it has; it halts that day's stock update entirely. The threshold is 90 percent of the target, or 180 stocks. If 179 come out, it stops.

The reason is that the list is not used only for updates. Every day Jupick deletes the documents of stocks not on the list. This cleanup keeps delisted stocks and stocks pushed down in market cap from staying on screen forever, and it trusts the list as the correct answer. If Jupick proceeded on a day when only half the listing data arrived, the cleanup would judge 100 perfectly healthy stocks to have vanished and delete them.

Proceeding with what is there when the data looks slightly off may seem considerate, but when that shortfall feeds a decision to delete, it is the opposite. Here stopping is the safe side. The stock screens that day keep yesterday's values, and that is better than a screen with 100 stocks gone.

Everything so far concerns the 200 Korean stocks. The 200 overseas stocks work differently. They are not drawn by rule every day; they sit in the code as a fixed roster.

The reason for not taking the top by market cap automatically is that the situation differs from Korea. US-listed stocks have no clue like the last character of a Korean stock code, so it is hard to tell common shares from other securities by code alone, and exchange-traded funds, REITs and depositary receipts get mixed into the market cap rankings. Automatic selection would first require rules to filter these out, and those rules do not exist yet.

So the overseas list differs in character from the Korean one. The Korean list is the result the market produced today; the overseas list is a roster a person set once. When market cap rankings change, the roster does not follow automatically. This difference is worth keeping in mind when looking at the Korean and overseas screens side by side.

Being on the list means the stock is in the top 200 by market cap as of today and did not hit any of the exclusion rules above. Nothing more. Being large and being good are different matters, and in fact many stocks on the list have grades C and D. The selection rules and the grade calculation do not refer to each other.

Conversely, not being on the list does not make a company a poor one. It is only outside the top 200, or a preferred share, or on KONEX, or has SPAC in its name, or there was a problem with that day's listing data. Absence from the screen is not an assessment of the company but information about the scope of this screen.

It is also worth remembering that the list is redrawn every day. Stocks near 200th place in market cap move in and out over a few days. If a stock seen yesterday is gone today, it is usually one on that boundary.

This content is for information only and is not investment advice. Jupick gives no trading advice on any stock, and inclusion in the list is not an endorsement of any kind. Investment decisions and responsibility for them rest with the user.