Primo is a subtheme of Duplo that consists of 8 sets that ran from 1995 to 1996. Most sets were released in 1996 which accounted for 4 sets. As of today, the average annual growth of all the sets in Duplo Primo is around 8.1% per year.
The LEGO DUPLO theme was introduced as far back as 1969 and is designed for children ages 1 to 5. It features DUPLO figures which are much larger than minifigures and DUPLO blocks which are about twice the length, width, and height of a standard System brick. Like LEGO System, DUPLO also has subthemes that are often junior versions of System themes, like Pirates and Castle and licensed themes like Disney and Super Heros.