Criteria of Kraljic's Purchasing Portfolio Matrix

Dear All, For my PhD project, I am trying to determine which criteria and factors should be included for two dimensions of well-known Kraljic's Purchasing Portfolio Matrix. The ones I have collected so far from the original Kraljic’s article (marked with *) and also from other sources are listed below with no order of importance. I appreciate your comments on proposed criteria and also any other extra criteria you may suggest with a short explanation. Thank you in advance. STRATEGIC IMPORTANCE OF PURCHASING (or IMPACT ON PROFIT) • Volume/monetary value of purchases (*) • Percentage to total purchase cost (*) • Switching costs (*) • Impact on end product quality/reliability (*) • Impact on business growth (*) • Impact on competitiveness • Additional value on product differentiation • Impact on production or supply network continuity COMPLEXITY OF SUPPLY MARKET (or SUPPLY RISK) • Product availability/scarcity (*) • Number of suppliers (*) • Entry barriers for new suppliers (*) • Storage risks (*) • Competitive demand (*) • Rate of technological advances (*) • Product substitution possibilities (*) • Make-or-buy opportunities (*) • Supplier substitution possibilities • Price volatility • Cost structure complexity • Environmental risks • Legal requirements • International trade risks • The complexity of supply network at Tier 2 and Tier 3 level