Which iud has the highest efficacy: mirena, skyla, or kyleena? why is the kaplan-meier for kyleena so much higher than the others at 1.45?

Similiar: Mirena, Skyla and Kyleena are all over 99% effective. However, Mirena initially releases 20 mcg/day of Levonorgestrel; Kyleena 17.5mcg/day and Skyla 14mcg/day. The higher dose may give Mirena a slight edge but its unproven. Mirena and Kyleena use is 5 years; Skyla 3 years. Skyla and Kyleena are smaller so insertion is less painful if you've never given birth. Best wishes!