I am looking at the following data set:

Month: 2007: 2006: Percentage change
JAN 1,189 1,193 0%
FEB 1,249 954 31%
MAR 1,135 1,278 -11%
APR 1,046 1,257 -17%
MAY 748 1,188 -37%
JUN 1,058 1,343 -21%
JUL 849 1,170 -27%
AUG 1,126
SEP 1,346
OCT 1,309
NOV 1,377
DEC 1,432

I would like to insert a trend line that might give a clue to the performance for the remainder of the year. If I select the default trend line it is a very sharp decline. I tried the moving average option and played with the different periods, but I really don't know what these mean. Other options are Logarithmic, Polynomial, Power and Exponential. I also tried just taking the percentage difference in the most recent four month period and applying that to the remainder of the year. Does anyone have any guidance on the best trend line option? Can anyone tell me what selecting the periods actually does.

Thanks for any help.

Jon