Pensions are funded from employee pauy.
Welfare for retirees without sufficient savings are paid from tax revenues. 
OAS was $20b/year 15 years ago, $60b/ year this year and $100b/year in 5 years. Part of that is demographics but a much larger part is that people are now saving an average 2.5% of pay for their retirement when that number was 18% in 1980.