## 2 Background and State-Of-The-Art  
Issues related to efficiency and productivity in construction are widely discussed and presented from different perspectives and at different levels. They are addressed as problems of the construction industry branch, construction projects, specific technologies, or the use of resources. In [1], the authors presented a comprehensive study and review of numerous works investigating factors affecting construction productivity. The study of works published over 30 years allowed them to point out a set of factors influencing productivity in the construction industry regardless of differences in various countries. These are: \"non-availability of materials, inadequate supervision, skill shortage, lack of proper tools and equipment, and incomplete drawing and specifications.\" They stated that some factors, namely, \"implications of technology, site amenities, process studies, project culture, and impacts of physiological and psychological factors\", have not been thoroughly investigated so far. The further paper [2] contributes to the construction management body of knowledge by providing a comprehensive review of different productivity monitoring techniques. The authors' findings are that the most adopted data acquisition techniques are traditional, computer vision-based, and photogrammetry-based methods. These are being combined with machine learning and BIM for the purposes of automated monitoring of construction productivity. Another work [3] focused on quantifying time waste in the architecture engineering construction industry as an important factor that counteracts performance and efficiency. The study provides a synthesis of the findings presented in several publications, which showed that an average of 49.6% of the time in construction is wasted. The conclusion is that there is considerable potential for improvement and reduction of wasteful activities. There are also several studies aiming at the use of different methods and approaches for the purposes of construction productivity, efficiency and performance investigation. These are analytical hierarchy process (AHP) applications for the purpose of analysis and improving productivity [4], descriptive and regression analyses along with a co-relational study for investigation of training and motivation practices effects on teamwork improvement and tasks efficiencies [5], performance metrics analysis and comparison with the use of queuing theory followed by simulation experiments for quantitative analysis of rate-driven and due date-driven residential buildings projects [6], the introduction of lean-based flow optimisation and Industry 4.0 concepts and principles for improving the efficiency of road construction [7]. Literature studies have shown that labour efficiency in construction is a widely discussed topic. The efficiency is being investigated with regard to the conditions and distinct character of regional and national construction markets. Several works have investigated this topic, including cases of European countries [8], specifically Poland [9], the United States of America [10], China [11], Turkey [12], Kuwait [13], Jordan [14], Uganda [15], Egypt [16], and Zimbabwe [17], which have presented broad analyses of factors affecting labour efficiency. From these works, it can be concluded that although some factors are common, there are strong regional influences on the attitude towards the problem. There is also a significant amount of attention given in published research to the relationships between different factors and the efficiency of construction works. The focus is on the influence of either certain specific factors or sets of factors on efficiency. However, the research is predominantly carried out at a country level. In [18], the authors investigate the relationship between change orders and labour efficiency. They develop a statistical dependency capable of estimating the actual amount of labour efficiency lost due to change orders.