how to populate null values as blank in cell

Hi All,

I have an query i have data like blow

and i want result like below

for % age change i have applied the previous function

formula is (data/previous(data)) -1*100

but is coming like below

for the 1 column i am getting 0% age due to i applied previous function but i don't have data for 2008

so i am trying  not to populate 0% for the % change before 2009

I have checked with null value 

If (IsNull(Previous [data])) then "" else ([data]/previous[data]) -1*100

so it is populating blanck value but i can not formatting the values as %age

please suggest 

how can i solve this issue please advice

Thanks in advance

Ranjeet