Where did you get this information? Keep in mind that they are reviewed annually. "Review" does not mean raised, lowered or changed at all. Rates can be reviewed and left as is.
It's also important to remember that just because the cost of living goes up or down in a given location does not mean an automatic increase or decrease in PLD. What matters is the increase/decrease of a given area compared to the baseline. If the cost of living goes up across the country, PLD essentially stays the same. General increases in cost of living are covered by general pay increases, not PLD. Furthermore if the cost of living in one location goes up, but at a lower rate than the baseline, then the PLD at that location will actually go down. Conversely, if the cost of living at a given location decreases at lower rate than the baseline, then PLD will go up at that location.