The population grows tremendously. During the census of 1960, one year after its creation as a municipality, Quezon had a population of only 5,797. Its population increased to 7,271 in 1970 and 8,225 in 1975 with an annual growth of 2.25% and 2.49% respectively. The tremendous increase of population began in 1975 to 1980 where population grows to 9,820 or 3.61% growth rate. Between the 1980s and 1990s, its population grew by 16,280 with an annual growth of 5.18%. Such an increase may be attributed to natural increase and influx of migrants particularly land seekers coming from various provinces (mainly from nearby Kalinga) with the operation of Chico River Irrigation System in 1983 that propelled the agricultural boom of Quezon. Population growth between 1990 and 1995 slowed down to 1.59% with 17,617 on record. The growth rate between 1995 and 2000 regained an increase of 2.66% when the local economy improved due to the concreting of the national highway and the increased remittances of its Overseas Filipino Workers (OFWs) working as either professionals or skilled workers in various fields in the Middle East, USA, Canada, London (UK), Hong Kong or Singapore.