知識社｜超市篇02｜點解超市貨品價格有些沒有整數？ | Knowledge Society Supermarket 02 | Why Do Supermarket Prices Often Avoid Round Numbers?
你有冇留意，超市貨架上好多價格都唔係整數，例如 $9.99、$19.90、$29.95？明明只差幾個仙，點解零售商唔直接寫成 $10、$20、$30？原來價格尾數背後，有一套幾有趣嘅消費心理。
Have you ever wondered why supermarket prices so often stop just short of a round number? A product may cost $9.99 instead of $10, or $19.95 instead of $20. The difference seems tiny, yet those final digits can influence how shoppers perceive value, compare products, and make quick purchasing decisions.
中文版本
行超市嗰陣，你可能已經習慣咗見到 $9.99、$19.99、$29.95 呢類價格，甚至已經完全唔覺得有咩特別。你可能會諗：「$9.99 同 $10 有咩分別？咪只係差一個仙囉。」從實際付款金額嚟講，的確只係差一個仙，但從消費者心理角度，兩個數字未必會被完全當成一樣。呢種做法叫做「9字尾定價」或者「心理定價」，零售商會利用價格接近一個整數但又未正式跨過去嘅特點，令消費者對價格產生不同感覺。研究發現，當價格由 $2.99 變成 $3.00，雖然只增加一仙，但因為最左邊嘅數字由「2」變成「3」，消費者有時會感覺兩個價格之間嘅差距比實際更加明顯，呢種現象被稱為「左位數效應」。 即係話，當你快速望貨架價格時，大腦未必會先慢慢計算完整數字，而可能先注意最左邊嘅主要數字。$9.99 望落去仍然係「9字頭」，$10.00 就正式進入「10字頭」。所以「$9.99」喺心理上可能會被歸類為「九蚊幾」，而唔係「十蚊」。當然，呢個效果並唔係每一個人、每一種產品都一樣強，亦唔代表所有人見到 $9.99 就一定會買。零售研究顯示，9字尾價格嘅效果會受到產品種類、價格水平、品牌、購物目的等因素影響，並唔係將所有價格改成 .99 就一定可以增加銷售。 更有趣嘅係，9字尾價格之所以令人產生「比較平」嘅印象，可能同消費者過去累積嘅經驗有關。好多促銷商品長期使用 $9.99、$19.99 呢類價格，消費者慢慢就將「9字尾」同「抵買」、「優惠」聯繫起來。研究一個大型美國連鎖食品店超過9,800萬個價格資料時，更發現9字尾價格並唔一定真係較低；某些情況下，9字尾價格甚至可以比非9字尾價格高出不少。換句話講，「睇落似平」同「實際比較平」係兩回事。 呢一點其實非常值得超市顧客留意。假設貨架上有兩包類似產品，一包 $9.99，另一包 $10.00，實際差距只有一仙，但你第一眼可能會自然覺得前者屬於「九蚊幾」嘅產品。再假設一件產品由 $19.99 加價到 $20.00，對商店嚟講只係增加一仙，但消費者見到價格由「19」跳到「20」，心理感覺可能會完全不同。正因如此，價格尾數並唔只係會計數字，而係零售設計其中一個細節。超市每日面對大量商品，顧客亦唔可能逐件產品慢慢比較，所以價格標籤往往要喺幾秒鐘之內傳遞「平」、「優惠」、「正常價」或者「高級」等訊息。亦唔係所有商品都適合使用 .99。有研究指出，對某些高級品牌或需要強調品質嘅商品，9字尾未必有利，甚至可能影響產品形象；相反，較低價、較新或者較弱勢品牌嘅產品，有時更加容易受益。 而且近年研究亦提醒大家，價格尾數嘅心理效果未必永遠強烈，研究方法、產品情境同消費者注意程度都可能改變結果。 所以，下次行超市見到 $9.99，唔需要即刻覺得「平一蚊」，因為實際上佢只係平一仙。真正值得做嘅係望多一眼：同類產品係幾多錢？每100克、每公升或者每件實際成本係幾多？有冇促銷條件？當你開始由「睇價格尾數」變成「比較真正價值」，你就會發現，超市價格牌其實唔只係告訴你要畀幾多錢，亦可能正在影響你點樣理解呢個價格。原來貨架上一個小小嘅「9」，背後都可以藏住一個幾有趣嘅零售心理學世界。
English Version
Walk through almost any supermarket and you will quickly notice something unusual about the prices. Many products do not end with a clean, round number. Instead of $10.00, you may see $9.99. Instead of $20.00, there might be $19.99 or $19.95. Financially, the difference can be tiny, but psychologically the two prices can feel surprisingly different. This practice is often described as nine-ending pricing, charm pricing, or psychological pricing. One important explanation comes from the “left-digit effect”. Research has found that consumers can perceive $2.99 and $3.00 differently even though the numerical difference is only one cent. The change of the leftmost digit—from 2 to 3—can make the price feel as though it has crossed a much larger psychological boundary. This matters in supermarkets because shopping is usually a fast-moving activity. Customers walk through aisles, compare several brands, respond to promotions and make many small decisions in a short period of time. They do not necessarily stop to calculate every price precisely. When a shopper sees $9.99, the first impression may be that the product is still in the “nine-dollar” range. Once the price becomes $10.00, it enters a new mental category. The difference in actual money is almost meaningless, but the visual difference can be much more noticeable. However, it would be wrong to assume that every price ending in 9 automatically makes a product more attractive. Research in grocery retailing shows that the effect depends on the product category, brand, price level, store environment and the shopper’s situation. Nine-ending prices are not universally effective. There is another fascinating part of the story. Shoppers may have learned over many years to associate prices ending in 9 with discounts and bargains. If $9.99, $19.99 and similar prices repeatedly appear on promotional signs, people can gradually develop the impression that a 9-ending price means “good value”. But that association does not necessarily mean the product is actually cheaper. A major study using more than 98 million price observations from a large US grocery chain found that nine-ending prices were not always lower than other prices and, in some cases, were substantially higher. The researchers suggested that the bargain image of nine-ending prices can survive even after the actual pricing relationship has changed. This gives us an important lesson when shopping. Imagine two similar products on the same shelf. One costs $9.99 and the other costs $10.00. The difference is only one cent, but the first price may immediately feel like a “nine-dollar” purchase while the second feels like a “ten-dollar” purchase. Now imagine a product moving from $19.99 to $20.00. The financial change is still only one cent, yet the leading number has crossed from 19 to 20, creating a different psychological impression. Pricing therefore becomes more than a simple accounting exercise. It becomes part of the way a retailer communicates value. At the same time, nine-ending prices are not necessarily the best choice for every product. Research has found that their effectiveness varies, and premium products may sometimes benefit from round prices because a clean number can communicate a different image of quality or positioning. Recent research also suggests that the strength of price-ending effects should not be exaggerated. Results can depend on how carefully shoppers process the information and on the shopping context itself. So the next time you see $9.99 on a supermarket shelf, do not automatically think, “That is almost one dollar cheaper.” It is actually only one cent cheaper than $10.00. A better shopping habit is to compare the full price with competing products, check the unit price, look at the quantity, and consider whether a promotion really offers better value. Once you start looking beyond the final digit, the supermarket shelf becomes much more interesting. That tiny “9” is not simply part of a price tag. It can also be part of a carefully designed retail message about how you should perceive the price.
總評
超市價格尾數睇落只係幾個仙嘅差別，但「9」可以影響人對價格嘅第一印象。真正精明嘅消費者，唔係見到 .99 就覺得平，而係識得比較實際價值。
A price ending in 9 may look like a tiny detail, yet it can shape the way shoppers interpret value. Smart shopping is not about assuming every .99 price is cheap—it is about looking beyond the final digit and comparing the real value.
