The common characteristic of systems in which there is paid political advertising is that advertising is unlimited - parties and candidates can buy as much as they can afford - whereas free direct access broadcasts are limited to a pre-determined share.

But this is not always the case, and a number of countries that operate a mix of paid advertising and free direct access limit the share of the former in proportion to the latter. Canada has a system in which a ceiling is set on the amount of advertising time that each party can purchase, on a basis that is closely akin to systems elsewhere for allocating free direct access time.

It is, in fact, relatively unusual to find a system that is characterized solely by paid political advertising with no free direct access. For many years Finland was an almost solitary example in Europe, with most other examples to be found in the Americas.

Venezuela, for example, allows no political advertising on the two government broadcasting channels, but unlimited advertising on private commercial channels. Political parties generally appear to be prepared to pay the same rates as other advertisers. There is a state subsidy for spending on advertising. The electoral law authorizes the Supreme Electoral Council to contribute to parties' advertising campaigns. The way this has generally worked is that after the election the Supreme Electoral Council gives grants to parties that obtained at least 10 per cent of votes cast in congressional elections.

An extraordinary characteristic of the Venezuelan system is that the incumbent administration is also allowed to buy advertising. The administration's commercials are not allowed by law to promote the ruling party - but the government's and the ruling party's commercials can be broadcast one after the other creating a strong argument in favour of the incumbent. In 1978, the government spent almost as much on television advertising as the two main political parties. Venezuela has an extremely high level of spending on political advertising - according to some estimates the highest per capita rate in the world.[i]

The United States is the best-known example internationally of a system of paid political advertising. But contrary to first impressions, the US system is far from unregulated. Legislation limiting campaign donations has a particular impact on television advertising, which is by far the largest item in the campaign budget.

But that is not by any means the full extent of regulation. The Federal Communication Act of 1934 as amended requires broadcasters to offer to sell equal time to all candidates for federal office. This must be available at the lowest rate charged to non-political advertisers. Equal opportunity means that stations that sell time to one candidate must give the opportunity to others.[ii] These are important principles, which ensure that political advertising does not entirely become the preserve of those with the biggest campaign war chests. They have been emulated in political advertising regulations worldwide:

• Advertising is offered at the lowest rate.
• If advertising space is offered to one candidate it is offered to all.