The northern winter still has a way to run, but already there are signs of hope. The days are lengthening, the daffodils have poked their heads above the ground and you can once again have a lane to yourself in the swimming pool.

The new year's resolution crowd has abandoned the health clubs. They arrive as the year begins and soon go. We will not see them until September, when they return filled with a post-holiday determination to slim down and tone up, before disappearing again a fortnight later.

If you are a regular health club user, it is easy to be irritated by the temporary hordes puzzling over the machines or swimming, heads up, in the middle of the lane. Easy, but short-sighted, because irregular members make gyms possible for everyone else.

The economics of health clubs are simple: you need thousands of members who never come. The
gym could never accommodate them all if they did.

By paying their dues and seldom appearing, inactive members ensure health club owners have enough money to invest in aerobics halls and squash courts, while keeping membership fees at reasonable levels for the regulars.

There are other businesses where the owners count on only a small proportion of the customers using the service. Insurance is one; those DVD rental clubs where you pay a fee and order films one at a time are another.

Gyms are different because they require expensive sites, cannot outsource beauty treatments to Asia and need constant investment if their premises are not to look shabby.

London's gentlemen's clubs work on the same principle, except that shabby premises appear to be mandatory and the members do not see each other naked (at least not at the ones I have been taken to).

Gerald Ratner, the British businessman who ran a successful health club after losing his jewellery empire when he described some of
its products as “crap”, says about 30 per cent of his members dropped out each year.

Some clubs attempt to limit the attrition rate by telephoning inactive members and asking whether there is anything the club can do for them. Mr Ratner never thought this was a good idea as it might remind them that they were wasting their money.

It is a constant battle to attract new members, he says, and some clubs resort to desperate measures. He recalls seeing a gym representative outside Cape Town airport tearing banknotes in half, giving one piece to passing strangers and promising them the other if they came to look around. They did not even need to join.

He preferred to rely on discounting the joining fee (but never the monthly membership) and showing prospective members the heated outdoor pool. People demand a pool, he says, but most do not use it. Many clubs waive the joining fee altogether.

Mr Ratner estimates that about 5 per cent of his members used the gym every day and 50 per cent at least twice a week. That left half in that essential group who sign up but rarely come.

Two Californian academics, Stefano DellaVigna and Ulrike Malmendier, studied three US health clubs and discovered that 80 per cent of members used the gym so infrequently that they would have been better off paying the $10 fee for each individual visit. Many also left substantial gaps between their last visit and cancelling their membership.

In their paper, the academics concluded either that the gym members were making “time-inconsistent choices” or that they had “limited cognitive abilities”.

Of course, some people say the same about gym members. It is one thing to pay to use a swimming pool or a tennis court, but most of us know you could get half the benefit of the other facilities by walking up the stairs and all the benefit by running up them.

In his recent autobiography, Mr Ratner recalls taking his father to show off his club. Ratner Sr, who had never been to a gym before, looked at the members pounding away on a treadmill before asking: “What are they trying to achieve?”

No matter. Regular members go because they think it does them good, but they should not take their clubs for granted. Many gyms are having a difficult time. Most UK clubs are “in distress or struggling”, a banker told the Financial Times in November.

In the US, national chain Bally Total Fitness spent two months in Chapter 11 bankruptcy protection last year after its New York Stock Exchange listing was suspended.

Clubs need more help from the regulars to attract new members. My own club is offering a mountain bike to anyone who persuades two friends to sign up. This is silly. If we were happy riding mountain bikes around the city we would not need the gym.

Far better to offer anyone who introduces new members the free run of the place when it is closed to everyone else. The other members will not mind. They are never there.

北方的冬天仍會持續一段時間，而希望的跡象已經顯現。白晝在變長，水仙花已從地里探出頭來，而你又可以在游泳池里獨占一條泳道了。

在新年里信誓旦旦的那群人已經將健身俱樂部拋諸腦后。他們在新年伊始時現身，很快就會消失。然后我們一直見不到他們，直到9月份，當他們重返健身俱樂部時，滿懷著假日結束后的決心，想要瘦身，想要健壯，然后在兩周之內再一次消失得無影無蹤。

如果你是健身俱樂部的常客，你會很容易對這群“游擊隊”產生厭煩。這些人或是在健身器械的面前顯得一頭霧水，或是霸占著泳道的中央，一路昂著頭游來游去。厭煩他們容易，不過這有點短視：正因為這些會員隔三岔五才來一趟，其他的所有會員才能得以健身。

健身俱樂部的生意經也比較簡單：你需要有上千名從不會光顧的會員。如果大家都來了，現有的場館里根本就裝不下。

繳納了會費，但極少現身，這些不活躍的會員能確保俱樂部的老板們掙到足夠的錢，去投資有氧體操房，或是壁球室，同時還能讓那些常客們的會費維持在合理的水平。

其它一些商業領域也有這樣的情況：老板指望有一小部分的客戶會使用服務。保險業是一種；繳納會費點片看的DVD出租俱樂部則是另一種。

但健身房則有所不同，因為它們需要租用昂貴的場地，不能把美容理療外包給亞洲，而且為了不讓場地顯得寒磣，它們還需要進行經常性的投資。

倫敦男士健身俱樂部的運營法則也與此相同，唯一例外是，場館似乎不可避免地破舊不堪，而會員們也不必看到對方赤身露體的樣子（至少別人帶我去的那些俱樂部是這樣）。

英國商人杰拉爾德•拉特納(Gerald Ratner)經營著一家成功的健身俱樂部。在此之前，他曾將原本經營的一些珠寶產品形容為“廢物”，從而終結了自己一手打造的珠寶王國。拉特納表示，每年他都有30%的會員出局。

一些俱樂部會給不活躍的會員打電話，問俱樂部能否為他們做些什么，從而試圖限制損耗率。但拉特納從不認為這是一個好主意，因為這會提醒那些人，他們正在浪費錢。

他說，吸引新成員是一場持久戰，一些俱樂部會無所不用其極。他回憶，有一次在開普敦機場外見到一位健身房促銷員，那個人當時把鈔票一撕兩半，給過路的陌生人每人發上一張，并承諾如果他們來健身房看看的話，就能得到另外半張。他們就連入會手續都不需要。

拉特納則更愿意通過入會費打折的辦法（但對月卡會員絕不這么做），或是向那些潛在會員展示一下加熱的戶外游泳池。他說，人們都需要一個游泳池，但多數人都不會去用它。另有許多俱樂部則免除入會費。

拉特納估計，在他的俱樂部中，約有5%的會員每天都在使用場館，另有50%的會員至少一周來兩次。剩下近一半的人只是簽名入會，但很少光顧。

加利福尼亞的兩位學者斯特凡諾•德拉維尼亞(Stefano DellaVigna)和烏爾麗克•馬爾門迪爾(Ulrike Malmendier)研究了3家美國健身俱樂部后發現，有80%的會員極少使用健身房，以至于如果他們單次支付10美元的費用，也許還更省錢。還有許多人從上一次健身到取消會籍的間隔時間非常長。

在這兩位學者的論文中，他們得出的結論是：要么是健身房的會員們做出了“時間不一致的選擇”，要么就是他們的“認知能力有限”。

當然，有些人對健身房會員也持相同的說法。付費去使用游泳池或網球場是一回事，但我們大多數人都知道，通過走樓梯你就能得到其它健身設施所能提供的一半好處，如果跑步上下樓梯，你就能得到所有的好處。

在近期的自傳里，拉特納回憶帶自己父親到俱樂部炫耀的情景。老拉特納以前從未進過健身館，他看見在跑步機上跑得咚咚作響的會員們，然后問道：“他們想干嗎？”

不要緊。健身館的常客們之所以經常光顧，是因為他們認為這樣對自己有好處，但他們不該認為參加俱樂部就理當如此。許多健身館的日子也不好過。一位銀行家在11月份時向《金融時報》透露，多數的英國健身俱樂部或是“陷于困境”，或是在“苦苦掙扎”。

在美國，全國連鎖的倍力健身(Bally Total Fitness)去年被紐約證交所(NYSE)停牌，然后處于破產保護狀態下兩個月的時間。

俱樂部需要常客提供更多的幫助來吸引新會員。我自己所在的俱樂部就承諾，向任何成功勸說兩位朋友入會的會員提供一輛山地車。這是個蠢辦法。如果我們騎著山地車滿城跑得很高興的話，誰還需要健身館呢。

最好的辦法是：向那些介紹新會員的人提供不對外開放時段的全免優惠。反正別的會員也不會介意。因為他們從不去那里。