What type of pension plan usually provides better protection against inflation up to the time...

Defined benefit pension plans base retirement income on formulas that may use:

Career average earnings → lower protection against inflation.

Final average earnings (last few years of salary) → better protection against inflation, since the calculation reflects recent, higher earnings that have already adjusted for inflation.

Defined contribution and group RRSPs do not guarantee inflation-adjusted benefits.

Thus, the Final average pension plan offers better inflation protection before retirement.