Keywords: 
• Night-time light remote sensing /
• Mann-Kendall trend test /
• Rank-size law /
• Pakistan /
• regional development

Abstract: It is important to know the pattern of Pakistan's regional development for the construction of the China-Pakistan Economic Corridor. In this paper, we used the Visible Infrared Imager Radiometer Suite (VⅡRS) night-time light remote sensing image as the main data source, and implemented the Savitzky-Golay (SG) filtering algorithm to repair the missing values of the images. Three methods, Night-time Light Change Ratio (NLCR), Mann-Kendall (MK) trend test method, and rank-scale law, were carried out to study the nighttime light change patterns of Pakistan's provincial/city level, geographic grid level, and East-West zone in three geographic scales. The analysis of the NLCR shows that from 2012 to 2019, the entire Pakistan has night-time light growth by 47.96%; all provincial regions have different degrees of development, and with NLCR increasing by >15%; the NLCR of Gwadar Port is 126.94%, which is the highest among the 15 node cities on the east and west lines of the China-Pakistan Economic Corridor; more importantly, not all 15 node cities have similar positive night-time light growth, with two cities having night-time light decrease. This indicates that the development of the 15 node cities on the east and west lines of the China-Pakistan Economic Corridor was unbalanced. Using the MK trend test, Punjab has the most spatial grids (1905) with the total night-time light upward trend at the 5 km geographic grid-scale, while Sindh has the most grids (338) with the total night-time light downward trend. Through visual inspection of the grids with the total night-time light downward trend in Sindh, it is found that most of the grids are located in rural areas of Sindh, which is consistent to the fact that there is a serious power shortage problem in rural areas of Sindh. The rank-size analysis results show that the distribution of urban size across the country has undergone a process from a relatively concentrated distribution to a more balanced distribution; the evolution of urban size distribution in the western region is also consistent to the national pattern; while the distribution of urban size in the eastern region has shifted from balanced to more balanced development; the Pareto indexes of both the eastern zone and the western zone are gradually decreased, indicating that the gap between the urban development in Pakistan is reduced, and the entire country is developing and becoming more balanced. In addition, It is worth noting that Pakistan's frequent large-scale power outages and lack of stable power supply may be the factors explaining the low brightness of night-time light in some areas. This study reveals Pakistan's regional development patterns under long-term time series and multiple spatial scales, which can provide a certain scientific basis for the planning of the China-Pakistan Economic Corridor.