The middle class in Portugal had long been growing in size but grew more rapidly beginning in the early 1960s as economic growth quickened. Depending on the criteria used, Portugal's middle class at the beginning of the 1990s could account for 25 to 30 percent of the population.

The traditional principle of political science states that the growth of a middle class brings greater social stability and better chances for the flourishing of democracy. However, the correlation of middle-class stability and democracy does not necessarily hold in Portugal. The reason for this lack of correlation stems from the fact that "middle class" in Portugal has two definitions. One definition is based on social and cultural criteria and the other on economics. The definition using economic criteria is the easiest to state: everyone above a certain income level but below another income level is middle class. This criterion would include some less wealthy professionals, business people, soldiers, government workers, small farmers who own their own lands, clerks, and better-off industrial workers. This list includes a large variety of persons of diverse occupations with little connecting them in terms of education, family background, or political values.

According to the socio-cultural definition of middle class, persons belonging to the middle class do not engage in manual labor, disdain it, and tend to feel a sense of superiority to those below them in the social hierarchy. The social-cultural definition regards professionals, business and commercial elements, military officers, and government workers as middle class, but not the enlisted, farmers, or industrial workers, no matter what their earnings. This latter definition of middle class results in a smaller group, more homogeneous in outlook than that resulting from purely economic criteria.

If the older, more traditional variety of middle class with its essentially aristocratic values (disdain for manual labor, for example) proved to be the prevailing model even in the 1990s, Portugal would remain essentially a two-class society divided between those who work with their hands and those who do not. A two-class society increases chances for division, class conflict, and even civil war. By contrast, the emergence of a large and independent middle class defined by economic categories rather than socio-cultural traits favors the growth of social pluralism and political stability. As both definitions of the middle class were employed in Portugal, predicting the country's future was more difficult than elsewhere in Western Europe.

An indication that economic criteria had greater validity than in the past was that Portugal's middle class, traditionally deeply divided on a host of social and political issues, increasingly voted on a more consistent basis for the moderate, centrist Social Democrat Party (Partido Social Democrata--PSD). The PSD had come to be seen by its foes, as well as its supporters, as a "bourgeois" party. The Portuguese working class, in contrast, has voted increasingly for the Socialist Party (Partido Socialista--PS), although18d gh the Portuguese Communist Party (Partido Comunista Português--PCP) also won some of its votes.

Data as of January 1993