an additional poverty line is based on of the median income measured in income reference year and is then uprated with inflation for all the intervening years contemporary poverty lines are sensitive to sudden shifts in the income distribution median household income may fall during an economic downturn reducing the poverty line and resulting in an artificially lower child poverty rate even if the number of poor children remains the same anchoring the poverty line in in real terms helps circumvent this limitation by keeping the threshold fixed at a moment in time rather than allowing it to move with the current income distribution