The effect of substitution bias is that the rise in the price of a fixed basket of goods over time tends to the rise in a consumer’s true cost of living, because it doesn’t take into account that the person can substitute between goods according to changes in their relative prices.

The correct answer is: overstate

Explanation:

The substitution bias in economic index numbers appears when the possibility of a consumer  to change the consumption of a good - that has become more expensive relative to others - for a cheaper one, is ignored. Thus, looking at the CPI (Consumer Price Index), as an indicator of how much the consumer cost of living has raised over time, without eliminating the substitution bias, can over-estimate this inflation effect.

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