# The Gap between the Admitted and the Measured Technical Debt: An Empirical Study
## 2 The State-of-the-Art While Measuring Technical Debt  
Technical debt is a well-known term that is used widely in current research. In our systematic literature review (SLR), implemented in early 2022, we investigated the state-of-the art and novelties in the field of technical debt measurement, supplemented by identifying existing research gaps within the domain. The goal was to gain an overview of the different aspects of measuring technical debt, investigating existing approaches, defined methods, used techniques, and available tools for measuring technical debt. The SLR was implemented using six different digital libraries: ScienceDirect, IEEE, Scopus, ACM, SpringerLink, and arXiv. The purpose was to detect any existing research on the following topics:  
* Possible ways to measure, identify, estimate, assess, calculate, evaluate, or quantify technical debt;
* Available tools used for measuring technical debt; and
* Investigating accuracy in the area of technical debt measurement. Based on the research focus, the search strings were formed, addressing different views of the implemented review. The search was conducted using the following aggregated search string:  
_(\"technical debt\") AND (\"estimate\" OR \"calculate\" OR \"assess\"\" OR \"identif\" OR \"measure\" OR \"quantif\" OR \"evaluat\") AND (\"method\" OR \"approach\" OR \"technique\")._  
The results of the SLR were as follows:  
* The first phase, _initial search_, while implementing the _inclusion_ and _exclusion criteria_, resulted in a set of **1282 studies**;
* The _second review phase_ included removing possible duplicates, performing title, summary, and keyword-based screening. It resulted in **28 studies** appropriate for inclusion in the next phase of the review;
* The _full-text review_ was the third phase of the SLR. Directly, it provided a set of **11 primary studies**;
* Finally, in the last phase, **additional studies** were included by employing a related work review. This is how we finished the review with **14 primary studies** in the field. Different technical debt domains were identified based on the presented search strings. A variety of research directions within the technical debt domain were also confirmed by [PERSON] et al. [5]. A precise estimation of technical debt is still under severe empirical and experimental inquiry [5]. According to the research by [PERSON] and [PERSON] [6], there are difficulties in assessing technical debt or the maintainability of a system. As the authors claim, these two concepts are not easy to understand and are not directly measurable. [PERSON] [7] proposed that technical debt is presented as a ratio instead of using an abstract value. Using the ratio, considering complete project effort, increases understanding and the possibility to compare technical debt values. Therefore, we also use it in this paper. [PERSON] et al. [8, 9] conducted a systematic mapping study, identifying techniques and approaches that can be used in technical debt management. According to [PERSON] et al. [9], among the identified steps of technical debt management is quantity debt estimation using methods or dedicated tools. On the other hand, [PERSON] et al. [8] stated that the central artefacts of technical debt management are technical debt items, an estimate of the amount of principal, an estimate of the amount of interest, the probability of interest repayment, and the impact of technical debt. The authors also studied technical debt measurement. [PERSON] et al. [10] presented the Jitterbug tool. The tool first identifies easy-to-find debts, which is followed by intelligent help for developers while discovering the remaining debt items manually. This work motivation was an insufficient precision and recall in identifying self-admitted technical debt (SATD) in the current automated solutions, preventing thorough process automation. [PERSON] et al. [11] mention different ways for estimating the technical debt principal using structural proxies and monetised proxies.