1 year; there is no year 0
The answer is nothing because there is no year 0.
-2 ,+2, -2 ,+2 etc ......
eleven thousand, one hundred eleven.
To find out you do Y2-Y1 over X2-X1....1-(-1)/-1-1......1-(-1)=2-1-1=-2the slope is 2over-2