What is Amount of volumetric polymerization shrinkage seen in composites during curing is: and explain in detail?
Linear shrinkage is about 0.2 to 2%.
Volumetric shrinkage is 1.7-5.7%.
Shrinkage is seen towards the centre in self cure materials and towards the light source in light cure materials. 
Reference : Nisha Garg 2ND ed Pg: 310