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.

北方的冬天仍会持续一段时间，而希望的迹象已经显现。白昼在变长，水仙花已从地里探出头来，而你又可以在游泳池里独占一条泳道了。

在新年里信誓旦旦的那群人已经将健身俱乐部抛诸脑后。他们在新年伊始时现身，很快就会消失。然后我们一直见不到他们，直到9月份，当他们重返健身俱乐部时，满怀着假日结束后的决心，想要瘦身，想要健壮，然后在两周之内再一次消失得无影无踪。

如果你是健身俱乐部的常客，你会很容易对这群“游击队”产生厌烦。这些人或是在健身器械的面前显得一头雾水，或是霸占着泳道的中央，一路昂着头游来游去。厌烦他们容易，不过这有点短视：正因为这些会员隔三岔五才来一趟，其他的所有会员才能得以健身。

健身俱乐部的生意经也比较简单：你需要有上千名从不会光顾的会员。如果大家都来了，现有的场馆里根本就装不下。

缴纳了会费，但极少现身，这些不活跃的会员能确保俱乐部的老板们挣到足够的钱，去投资有氧体操房，或是壁球室，同时还能让那些常客们的会费维持在合理的水平。

其它一些商业领域也有这样的情况：老板指望有一小部分的客户会使用服务。保险业是一种；缴纳会费点片看的DVD出租俱乐部则是另一种。

但健身房则有所不同，因为它们需要租用昂贵的场地，不能把美容理疗外包给亚洲，而且为了不让场地显得寒碜，它们还需要进行经常性的投资。

伦敦男士健身俱乐部的运营法则也与此相同，唯一例外是，场馆似乎不可避免地破旧不堪，而会员们也不必看到对方赤身露体的样子（至少别人带我去的那些俱乐部是这样）。

英国商人杰拉尔德•拉特纳(Gerald Ratner)经营着一家成功的健身俱乐部。在此之前，他曾将原本经营的一些珠宝产品形容为“废物”，从而终结了自己一手打造的珠宝王国。拉特纳表示，每年他都有30%的会员出局。

一些俱乐部会给不活跃的会员打电话，问俱乐部能否为他们做些什么，从而试图限制损耗率。但拉特纳从不认为这是一个好主意，因为这会提醒那些人，他们正在浪费钱。

他说，吸引新成员是一场持久战，一些俱乐部会无所不用其极。他回忆，有一次在开普敦机场外见到一位健身房促销员，那个人当时把钞票一撕两半，给过路的陌生人每人发上一张，并承诺如果他们来健身房看看的话，就能得到另外半张。他们就连入会手续都不需要。

拉特纳则更愿意通过入会费打折的办法（但对月卡会员绝不这么做），或是向那些潜在会员展示一下加热的户外游泳池。他说，人们都需要一个游泳池，但多数人都不会去用它。另有许多俱乐部则免除入会费。

拉特纳估计，在他的俱乐部中，约有5%的会员每天都在使用场馆，另有50%的会员至少一周来两次。剩下近一半的人只是签名入会，但很少光顾。

加利福尼亚的两位学者斯特凡诺•德拉维尼亚(Stefano DellaVigna)和乌尔丽克•马尔门迪尔(Ulrike Malmendier)研究了3家美国健身俱乐部后发现，有80%的会员极少使用健身房，以至于如果他们单次支付10美元的费用，也许还更省钱。还有许多人从上一次健身到取消会籍的间隔时间非常长。

在这两位学者的论文中，他们得出的结论是：要么是健身房的会员们做出了“时间不一致的选择”，要么就是他们的“认知能力有限”。

当然，有些人对健身房会员也持相同的说法。付费去使用游泳池或网球场是一回事，但我们大多数人都知道，通过走楼梯你就能得到其它健身设施所能提供的一半好处，如果跑步上下楼梯，你就能得到所有的好处。

在近期的自传里，拉特纳回忆带自己父亲到俱乐部炫耀的情景。老拉特纳以前从未进过健身馆，他看见在跑步机上跑得咚咚作响的会员们，然后问道：“他们想干吗？”

不要紧。健身馆的常客们之所以经常光顾，是因为他们认为这样对自己有好处，但他们不该认为参加俱乐部就理当如此。许多健身馆的日子也不好过。一位银行家在11月份时向《金融时报》透露，多数的英国健身俱乐部或是“陷于困境”，或是在“苦苦挣扎”。

在美国，全国连锁的倍力健身(Bally Total Fitness)去年被纽约证交所(NYSE)停牌，然后处于破产保护状态下两个月的时间。

俱乐部需要常客提供更多的帮助来吸引新会员。我自己所在的俱乐部就承诺，向任何成功劝说两位朋友入会的会员提供一辆山地车。这是个蠢办法。如果我们骑着山地车满城跑得很高兴的话，谁还需要健身馆呢。

最好的办法是：向那些介绍新会员的人提供不对外开放时段的全免优惠。反正别的会员也不会介意。因为他们从不去那里。