The dual labour market theory aims at introducing a broader range of factors into economic research, such as institutional aspects, race and gender. It divides the economy into two parts, called the "primary" and "secondary" sectors. The distinction may also be drawn between formal/informal sectors or sectors with high/low value-added. A broader concept is that of labour market segmentation. While the word "dual" implies a division into two parallel markets, segmentation in its broadest sense may involve several distinct labour markets.