The volume indices at NACE four-digit sector level are calculated by deflating value indices using the aid of the consumer price index for sector 45 and 47, and the price index of first-hand domestic sales for sector 46. From January 2002, volume indices at NACE two and three-digit sector level are calculated as a weighted sum of the volume indices at NACE four-digit sector level with value shares in the reference year as weight. In the past, volume indices at the NACE two and three-digit sector level were calculated using immediate deflation of value indices.