## 3 Results
### Factors That Affect the Demands for 22 Subcategories  
Using the random forest regression model, the importance of all the indicators that influence the elderly demand for services were analyzed and the top 10 indicators were ranked (Figure 6). The highest R\({}^{2}\) in the model was 0.75 for travel companionship, followed by home cleaning at 0.64, rehabilitation and physiotherapy at 0.65, and psychological counseling at 0.6, all of which are above 0.6. Those with R\({}^{2}\) below 0.5 included dining for the elderly at 0.46, errands and payment service at 0.46 as well, cultural and recreational activities at 0.47, and dispute resolution at 0.49, indicating that the fit was relatively poor. Nevertheless, certain patterns were still discernible. In general, among all the influencing factors with the highest importance in the 22 subcategories of demand,'mean distance from CECS to downtown landmark' occurred with the highest frequency, followed by \"living arrangements\" and \"area ratio of all CECSs to subdistrict\", belonging to characteristics of built environment and elderly themselves, with the former being more important. The second most important factors are \"occupation before retirement\", \"living arrangements\", \"caregiver\", \"age\", \"gender\", \"monthly disposable income\", \"mean distance from CECS to downtown landmark\", and \"housing prices\", which shows that the characteristics of the elderly themselves are more important than any others. The third most important factors were \"educational background\" and \"mean distance from CECS to nearest subway stations\". The first three positions of importance show that characteristics of the built environment, such as the accessibility of CECS, the locational advantage of the subdistricts where the elderly reside, and economic level affect their demand for elderly care services the most. Also, the elderly's attributes, such as age, living arrangements and economic status are also important factors. Statistics on the frequency of the top three, top five, and top ten factors (Figure 7) show that among the top three, the most frequent were \"mean distance from CECS to downtown landmark\", \"living arrangements\", and \"mean distance from CECS to nearest main roads\", followed by \"gender\", \"floor area ratio\", \"occupation before retirement\", and \"caregiver\"; in the top five, the most important ones were the same as in the top 3 group, with the addition of \"educational background\"; and in the top 10, the most important one was still \"mean distance from CECS to downtown landmark\", followed by \"living arrangements\", \"caregiver\", \"mean distance from CECS to nearest main roads\", and \"educational background\". \"Mean distance from CECS to downtown landmark\" was the most important factor we found, which reflects the fact that the location of a CECS as well as its transportation accessibility are both keystones for the acquisition of elderly services in city centers. Overall, the importance of activity characteristics among the attributes of the elderly was relatively low. Combining importance ranking with frequency of ranking, the relatively most important types of activities were \"singing\", \"walking\", and \"Tai Chi\", and the preferred place for activities was \"outdoor space in the community\". However, their importance was much lower than that of the elderly's own socio-economic attributes, and even less than built environment factors as well. In the top three subcategories with the highest level of demand, cultural and recreational activities, repair and troubleshooting, and emergency call service, the most important influencing factors were, respectively, \"housing prices\", \"mean distance from CECS to downtown landmark\", and \"occupation before retirement\". In the subcategories with a higher level of demand, such as physical exercise and companionship and comfort, the most important factors were mainly the characteristics of CECS (6 in 7), except for \"community pharmacy services\", which corresponded to \"living arrangements\".