Olympus XZ-2 iHS has a
12.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CMOS sensor . On the other hand, Nikon A1000 has a
16.0MP 1/2.3 (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Below you can see the XZ-2 iHS and A1000 sensor size comparison.
As seen above, Olympus XZ-2 iHS has a 1.5x Larger sensor area than Nikon A1000. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.