In 2009, when the population of a municipality defined in the second paragraph of Article L. 2334-2, authenticated at 1 January 2009, is 10% or more lower than in 2008, the basic allocation provided for in 1° of I of Article L. 2334-7 accruing to this municipality is increased by an amount equal to 50% of the difference between the amount of the basic allocation it received in 2008 and the amount of the allocation it should receive in 2009.