It's the chief actuary of Canada that does estimates for those expenditures.
Restoring the age of eligibility to 65 would increase OAS program costs by $11.6 billion in 2030, which is the first year it would be fully implemented. That takes into account the increase in July for the lowest-income seniors. It would move the OAS projected expenditures as a percentage of GDP by 0.33%, from 2.73% of the GDP up to 3.06%.