In the 1950s and 1960s, hawker centres were considered to be a venue for the less affluent. They had a reputation for unhygienic food, partly due to the frequent appearance of stray domestic pets and pests. Many hawker centres were poorly managed by their operators, often lacking running water and proper facilities for cleaning. Pressure from the government led to a vast improvement in hygiene standards. This includes the implementation of licensing requirements, where a sufficient standard of hygiene is required for the stall to operate, and rewarding exceptionally good hygiene. A score of 85% or higher results in an A, and the lowest grade is a D, which ranges from 40 to 49% passing standards. These grades are required to be displayed on hawker stands. Upgrading or reconstruction of hawker centres was initiated in the late 1980s to early 1990s in Singapore.