how do companies evaluate countries which are better for outsourcing

Global Services Location Index (GSLI)

This Index tracks the contours of the offshoring landscape in 50 countries across four major categories: financial attractiveness, people skills and availability, business environment, and the new digital resonance category explained in figure 1. It assesses countries' capacity to deliver BPO and ITO services based on 44 different metrics (see Appendix: About the study). 

One of the newly added items in it in addition to standard parameters associated with traditional IT outsourcing like financial attractiveness, people skills and availability, legal and cybersecurity environment is one of the key factors to account in decision making

https://www.kearney.com/digital-transformation/gsli/2019-full-report