Do installments always lose to a lump sum?

No. In a strongly rising market like this window, every later purchase carries a higher cost and the lump sum wins. Start near a peak and go through a long decline, and installments can come out ahead by lowering the average cost. Which market you are in only becomes clear afterward.

Are dividends included in this calculation?

No. Samsung Electronics pays quarterly dividends, so with reinvestment both approaches would end above the figures in this report.

What was the average cost across the 36 purchases?

79,758 won, about 19% above the 67,100 won close of the first purchase date. That is the direct cost of deferring purchases in a rising market.

What if you had bought 300,000 won of Samsung Electronics every payday for 3 years?

Mr. Latte

Published 2026-08-22 18:05 KST

A row of small coin jars on a wooden shelf, with one large jar full of coins at the end

We assumed 36 payday purchases of 300,000 won of Samsung Electronics from August 25, 2023 to July 27, 2026. The 10.8M won invested was worth 38.12M won at the August 21, 2026 close (+252.9%). The same 10.8M won invested all at once on the first payday would be 45.31M won (+319.5%). Over three strongly rising years, every deferred purchase raised the average cost, and the gap came to 7.19M won.

Hypothesis

“Buying a little every payday should end up roughly where a single lump-sum purchase does.”

Experiment setup

Buy 300,000 won of Samsung Electronics at the close of the 25th each month (next trading day if closed), 36 times in total. Dividends, fees and taxes excluded; fractional shares assumed.

First purchase: 2023-08-25
Valuation date: 2026-08-21
Total invested: ₩10.8M
Stocks: Samsung Electronics

Result

Final value

₩38.12M+252.9%

Hypothesis rejected

Payday installments₩38.12M

Same money, lump sum on day one₩45.31M · +319.5%

Trend chart

Unit: KRW

Payday installmentsDay-one lump sum

Month-end values. The installment line shows only the money already invested, so salary not yet contributed is not on the line.

Verdict

Hypothesis rejected

Monthly buying turned 10.8M won into 38.12M won, but putting it all in on day one would have made 45.31M won. Spreading out the timing cost 7.19M won in a market that kept climbing.

Why this experiment

Buying a fixed amount every month, the way you would fund a savings plan, is how most salaried investors actually buy stocks. People say spreading out your timing buys peace of mind, but the price tag of that peace is rarely computed. So we applied both approaches to three years of actual closing prices.

For a year and a half, the hypothesis looked right

While Samsung Electronics sagged through late 2024, installments looked like the smarter side. At the end of 2024 the lump sum was down to 8.56M won on a 10.8M won outlay (-21%), and the installment account was at 3.91M won on 5.1M won invested (-23%) but still had paydays left to deploy. This was also the stretch where it kept accumulating shares at lower prices.

The last year decided it

From late 2025 the share price ran from the 60,000-won range to the 280,000-won range, and the order flipped. The lump sum had all 160.9 shares bought at 67,100 won riding the entire move, while the installment plan's average cost had climbed to 79,758 won and its final-year purchases simply had no time to grow. Same money, same stock, and the timing choice alone separated the outcomes by 7.19M won.

There are markets where installments win

This does not mean installment buying is bad; it means spreading purchases is expensive in a market that only goes up. Start at a peak and ride a long decline, and installments pull ahead by lowering the average cost. Since you only know which market you got after the fact, spreading your timing is less a return-maximizing device than a regret-minimizing one. And a salaried worker never had the day-one lump sum anyway, so this comparison is really about someone who already holds the cash.

Key numbers

Purchases: 36
Average cost: 79,758 won
Shares accumulated: 135.4
First purchase close: 67,100 won (2023-08-25)
Valuation close: 281,500 won (2026-08-21)
Gap between the two: ₩7.19M

FAQ

Do installments always lose to a lump sum?: No. In a strongly rising market like this window, every later purchase carries a higher cost and the lump sum wins. Start near a peak and go through a long decline, and installments can come out ahead by lowering the average cost. Which market you are in only becomes clear afterward.
Are dividends included in this calculation?: No. Samsung Electronics pays quarterly dividends, so with reinvestment both approaches would end above the figures in this report.
What was the average cost across the 36 purchases?: 79,758 won, about 19% above the 67,100 won close of the first purchase date. That is the direct cost of deferring purchases in a rising market.

How this was calculated

Daily closing prices for Samsung Electronics (005930.KS) from Yahoo Finance. Purchases use the close of the 25th or the next trading day; the benchmark invests the full 10.8M won at the first purchase date's close (2023-08-25). Dividend reinvestment, fees, taxes and lot-size rules are excluded, and fractional shares are assumed. Samsung pays quarterly dividends, so including them would lift both outcomes above the figures here.

Data sources

[1] Samsung Electronics (005930.KS) daily prices · Yahoo Finance · 2026-08-21

Stocks in this report

These are hypothetical results computed from past prices. A real trade would differ with fees, taxes, lot sizes and execution timing, and past returns say nothing about future returns. This is not a solicitation to buy or sell any security. The money flow and stock signals this service shows are estimated, for-reference information based on price and volume. It is not a solicitation to buy or sell any security, nor investment advice. It is a prior-close daily batch, not real-time quotes, and all investment decisions and responsibility are your own. The Trade button is a convenience link to your chosen brokerage's app/website; orders are placed directly at the brokerage and InverseOne is not involved in any order.