the worst rent increase we had, was after 12months, they landlords let our lease roll onto periodical and 6 weeks after dd was born raised it by $80 a week. from $370 to $450. (talking 2006 here too). they wanted to sell the place and needed it to have a good rental income to make it appealing.
Needless to say we couldnt afford it after dropping to 1 wage, and moved out - within a week there were new tenants paying $450~!

supply and demand i guess