## 3 Data and Results  
### Date and Models  
In this study, the rate of technological change was calculated using the technical data of smartphones, which are evaluated to have a high rate of technological development. Smartphone manufacturers for this study are selected considering dual-use technology, global market share, and growth rate [15, 43, 44, 45, 46]. The main data sources are from the websites [[https://www.kaggle.com/msainani/gsmarena-mobile-devices](https://www.kaggle.com/msainani/gsmarena-mobile-devices)]([https://www.kaggle.com/msainani/gsmarena-mobile-devices](https://www.kaggle.com/msainani/gsmarena-mobile-devices)) (accessed on 13 February 2022) and www.gsmarena.com (accessed on 3 March 2022).  
The dataset, initially introduced by [PERSON] [45], has 10,105 observations that include performance and characteristics parameters of smartphone data that were firstly flown from 1994 to 2020. Missing values are supplemented if there is data provided by the GSMARENA site [46], and smartphone models with insufficient data necessary for analysis are deleted, and data are constructed focusing on representative models of each manufacturer. Table 1 shows the final smartphone dataset used for the analysis. The analysis of this study covered technical data of 107 smartphones released between 2005 and 2020.  
In the case of TFDEA application, an output-oriented VRS model was used in consideration of previous studies and the characteristics of the model [24, 25, 28]. The input variables are price and body weight, and output variables are network speed (ntwk), display resolution (resolution), battery capacity (btycpcty), sensors (sensors), CPU speed (cpus), and primary camera performance (pcamp).  
As analysis software, TFDEA R program of [PERSON] and [PERSON] [15] and Stata programs, dea.ado, tfdea.ado, malmq.ado, supereff.ado, of [PERSON] [16, 17, 42] were used in parallel.  
Smartphone specification data were selected in terms of performance required for the military use of commercial products of interest in this study, and input/output variables were determined as follows. Although it is the leading technology for commercial smartphones, the military requirement may be low, and conversely, it may not be considered important in commercial smartphones but may have high military requirements. In this study, performance variables in the military field were selected in consideration of the performance parameters of military radios presented in Jane's Defense Data Service (JDDS). The performance indicators of military radios included frequency range, operable channels, display performance, battery duration, sensitivity, weight, operable temperature, size, and audio output in common. Table 2 shows the input and output variables used in the analysis. [PERSON] [47] was referred to quantify qualitative variable values.  
* DMU: name of the smartphone
* year: year of smartphone introduction
* price: retail price announced in EUD
* bdywgt: body weight in kg
* ntwk: network bands in generation
* scrssize: display size in square inches
* resolution: display resolution in ppi
* sensors: sensors in generation
* ntwk:1: network speed in Mbps
* cpus: cpu speed in MHz
* pcamp: main camera performance in MP
* btycpcty: battery capacity in mAh
* comlev: WLAN in generation  
The screen of the smartphone takes over the role of a video display and information input device. There is a limit that it is difficult to use the communication function of a commercial smartphone in military operations, but there is no better alternative to a high-performance personal computer dedicated to information processing. It is of interest to see how the higher military requirements, such as military security requirements, than commercial products will affect the technological change of smartphones in the future.