In the data file, the source writes:

Data on the structure of enterprises in the construction sector have been revised for the period 2008 - 2012 due to methodological changes.

The revision can be attributed to two main factors, the improvements in the coverage of the sector in the Business Register and the treatment of subcontracting. More specifically:

1. a. The reconciliation of the Business Register to the definition of the “enterprise“ has led to the removal from the construction sector of certain statistical units that referred to the construction activity of public or semi-government organisations, such as the Public Works Department, the district administration offices, the Electricity Authority, the Telecommunications Authority etc.

1. b. The use of administrative records as the sole source of updating the Business Register has brought about changes to the sector’s population and unit reclassifications. In particular, the coverage of the self employed has significantly improved leading to a large increase in the population of the sector. Consequently, it was deemed necessary to recalculate the weighting coefficients that were used in the sample survey.
 
2. In the past, subcontracting was not included in the calculation of Gross Output (neither of Intermediate Consumption) so that the value of the Gross Output to be comparable with the total cost of construction of a project as estimated from the Building Permits and Housing Survey. In implementing the provisions of Regulation (EC) No. 250/2009 concerning the definitions of characteristics for structural business statistics, starting from the reference year 2008, subcontracting is included in Gross Output (and in Intermediate Consumption). Hence, this change has no effect on Value Added.

The above mentioned changes have led to the data as from 2008 onwards not being directly comparable to data for the previous years.