 Sarnia 's population experienced a continual growth from 1961 to 1991 , with a 1991 population of 74 @,@ <unk> . In 2001 the population had declined by approximately 3 @,@ 000 . Since 2001 Sarnia 's population has been growing slowly , with a 2011 population count of 72 @,@ 366 . Despite these modest gains , an April 2010 report " Sarnia @-@ Lambton 's Labour Market " states : " Large petrochemical companies are the community 's main economic drivers . Over the recent past , several plants have <unk> , and of those still in operation , increased <unk> and <unk> has led to significantly fewer workers . " . These <unk> and the resulting loss of jobs , and therefore population as workers search for employment elsewhere , will contribute to a general decline shown by one August 2011 study , which shows that the population will decline by 17 % over the next twenty @-@ five years . The Monteith @-@ Brown study cited outlines a plan for restructuring the city based on hybrid <unk> areas , which will bring work opportunities closer to the neighborhoods where people live . The City of Sarnia and Lambton County are also implementing an economic development plan with an emphasis on <unk> and renewable energy . 
