Whether supplier bargaining power represents a strong or weak source of competitive pressure is affected by

the number of suppliers of a particular item$--$greater than ten suppliers translates into weak supplier power, while fewer than ten suppliers translates into strong supplier power.

how fast the prices of the items being furnished by suppliers are rising or falling.

the extent to which industry members have strongly or weakly differentiated products.

whether the item being supplied is a standard item $($or commodity$)$ or$,$ instead, whether certain suppliers provide a differentiated input that enhances the performance or quality of the industry's product.

how long industry members have been closely collaborating with their key suppliers$--$long$-$term close collaboration greatly strengthens supplier bargaining power.