Either way, however, most media could not survive without income derived from advertisements. That means they need staff to sell their advertising space or time, who are just as necessary as those who produce the editorial matter.
The Advertisinq Association estimates that between 6,000 and 8,000 people work in media sales, covering television, radio, cinema, newspaper, magazine, directory, poster and transport advertising.
Sales staff are usually employed by media owners themselves, but in some cases by 'sales houses' or agencies that sell space or time on their behalf.
Airtime on ITV is sold not by individual regional companies but by three sales houses - Laser, TSMS and Carlton UK. There are also radio sales houses that sell nationally on behalf of local radio stations.
Whether the task is persuading someone to spend much of their advertising budget on the break in News at Ten or the sides of buses, it generally requires certain characteristics. 'Our clients are looking for people who are keen, determined, tenacious and can make an immediate impression,' says Paul Farrer of the recruitment consultancy Phee Farrer Jones. 'You can usually tell in about two seconds on the phone if someone can grab your attention in the right way.'
But within this, different personalities may be suited to different media.
At one extreme, according to Mr Farrer, 'you have commission-only directory publishers that publish things like the international directory of widget-makers. They give people a script, get them to ring up companies in the Czech Republic or somewhere, and if they can sell a page for pounds 7,500, they get 20 per cent. They are looking for very aggressive, 'I just want the money'-type people.'
Television represents the other end of the spectrum. Sales staff need not be foot-in-the-door types because the advertiser is generally happy to invite them in. It is often more a question of negotiating a price rather than persuading a sceptical listener of the benefits of the medium. In between are the places where many entrants to the industry start work - classified sections of business magazines and newspapers. Jobs with major publishers generally involve a basic starting salary of about pounds 10,000-12,000 plus commission, and proper training programmes.
For the first few months the job will consist of making dozens of phone calls a day, most of which will invariably be fruitless. After six months or so you might become a field sales executive, visiting clients and selling face to face. This might be accompanied by moving into selling display advertising or going from trade to consumer magazines. The emphasis shifts to building relationships rather than the quick sell. After this, there are management opportunities for the successful.
'Media sales gives the opportunity to progress very quickly for young graduates going into business,' says Gill Hollis of another recruitment consultancy, the Davis Company. 'You get very good training in the good companies, and someone with only six to nine months' experience can take on real responsibility. Employers promote quickly and recruit their managers from within to hang on to good people.'
She adds: ''There is a dearth of good media salespeople of one to three years' experience. Media directors often complain that they get either totally uninformed droning or types who just say, 'Shall we go down the pub now?'.'
Financial rewards can increase rapidly in terms of both salary and commission, and perks such as company cars and expense accounts. On the right newspapers, for example, you will find yourself taking clients on skiing holidays (although this is beyond the reach of the Independent).
Graduates who start work at TV or radio sales houses usually spend at least a year as sales assistants, doing administrative back-up work for salespeople, before they do any serious selling or negotiating themselves.
In due course those who sell TV airtime will be dealing in the largest sums and possibly making the most money, but it takes longer to progress up the career ladder than in other parts of the industry.
Media salespeople do sometimes move to the other side of the fence and become buyers for ad agencies or specialist media-buying comranies. 'Our staff get poached by ad agencies,' say's Sue Blakemore, a sales group manager at Carlton UK. 'Agencies don't train. They let someone else train.
After one to two years' experience our staff are eminently buyable.' But media sales is not a route into journalism or television production.
Many people who leave media sales quit the media industry altogether. This is true, for example, of 80 per cent of those leaving the magazine publisher VNU, which until recently has been a major graduate recruiter. It has now decided to recruit only staff who already have one year's sales experience.
Most of its former staff went to sales-related jobs, such as selling cars or property.
Newspapers tend to advertise sales jobs in their own pages, if only to show faith in their own medium. Other media companies may use one or more of the several firms of recruitment consultants that specialise in this area and screen applicants on behalf of employers. But in many cases vacancies are filled without advertising. Anyone seeking a job in media sales could register with two or three firms of consultants, but should approach employers in which they are interested directly. High turnover means opportunities are often available. And the manner of approach should demonstrate the qualities of assertiveness and persistence that employers are seeking.
'Some people send you a super CV, but then you don't hear from them again,' says Anna Coles, recruitment manager for Haymarket Publishing. 'I think sometimes they assume that I don't have any vacancies. But if they are the sort of person I really want, they wouldn't leave it at that, they'd phone me up.'
Further information: 'Getting into Advertising', available from the Advertising Association, Abford House, 15 Wilton Road, London SW1V 1NJ.