What causes the most propulsion in backstroke--arms or kicks

Some say in backstroke propulsion comes mostly from the arm movement, while others say kicking is the most important. What do you think? Is it possible to be fast (not the fastest) while being weak in one or the other? Agreed with Chris regarding the kick and the percentage of relevance. It may not be a contributing factor to propulsion, but it's an integral part of the stroke. And the kick doesn't have to be exhausting. Just enough to create a boil of water under the surface at one's toes. Ideally the way to make backstroke more efficient is to avoid swimming flat on one's back. And a steady flutter kick ensures you'll be able to achieve a long reach and decent shoulder roll with each catch and pull. Shoulder rotation is very noticeable on any good backstroker. And the legs are the support system for making it all come together.YouTube - Backstroke Technique - Side View - Krayzelburg, Phelps, Lochte

Some say in backstroke propulsion comes mostly from the arm movement, while others say kicking is the most important. What do you think? Is it possible to be fast (not the fastest) while being weak in one or the other? Agreed with Chris regarding the kick and the percentage of relevance. It may not be a contributing factor to propulsion, but it's an integral part of the stroke. And the kick doesn't have to be exhausting. Just enough to create a boil of water under the surface at one's toes. Ideally the way to make backstroke more efficient is to avoid swimming flat on one's back. And a steady flutter kick ensures you'll be able to achieve a long reach and decent shoulder roll with each catch and pull. Shoulder rotation is very noticeable on any good backstroker. And the legs are the support system for making it all come together.YouTube - Backstroke Technique - Side View - Krayzelburg, Phelps, Lochte