The green card, or the Alien Registration Receipt Card (it is in fact pink) is the best-known and most coveted of immigration documents. It entitles the holder to work and live permanently in the United States.

Significantly, the green card not only entitles you to live in the country - permanent residence is a necessity. If the INS suspects you of having another home abroad, and if you spend more than a certain amount of time out of the country (usually a year), you may lose your green card. You have to satisfy the authorities that you are, and mean to remain, a permanent resident.

This can cause problems if you want to apply for a visa and then for a green card, because a requirement of most visas is the absolute intention not to remain permanently. A certain amount of ingenuity is often needed to explain a sudden change in circumstances.

A green card holder is a tax resident of the United States, and has the right to apply for US citizenship after a certain time. One of the only differences between citizenship and green card status is that the latter does not give you the right to vote.

Everyone has an equal chance of getting a green card. Although some people consider that it is more difficult for a Western European to make a successful application, everybody applying through one of the normal channels (for example through employment, or as a family member of a US citizen) has the same status whatever their nationality. The fact is that many Western Europeans in the United States do not have green cards because they do not see themselves as permanent residents. It is more common for them to stay for the duration of a non-immigrant visa and to return periodically to their own country, whereas many people from the developing world and from Eastern Europe tend to come to America to stay for good.

Another reason for the lack of Britons with green cards is that for several years they have not been eligible for the Green Card Lottery (see below), which is only open to nationals of countries which have traditionally had lower levels of emigration to the United States.

Many Europeans in the USA complain about the system, its expenses and difficulties. One woman says: "British people and Europeans have a very hard time staying here, and have to move through the immigration system from one visa to another and finally to a green card. This is a very difficult process which I can testify to first hand. Many circumvent the system by marrying, although even then the immigration department checks up on them to see if the marriage is valid."

The only case in which certain nationalities are favored above others is in the Diversity Immigrant Visa program - popularly known as the Green Card Lottery (see below), by which 55,000 green cards are reserved each year for countries which traditionally have not sent many emigrants to the USA. The Immigration Act of 1990 introduced this category as a way of encouraging ethnic diversity in the US population. The odds of being selected are about one in twenty, according to the INS.

Certain categories are favored above others: the vital distinction is whether you come from a country with a repressive regime. Political refugees are given priority above many other categories. Other ways of getting a green card include investment in the USA, although as a minimum of $500,000 must be invested it is not an option open to many.