OK, you lost me. How can panel conversion efficiency be one of the least important drivers of the solar industry?
The only thing that higher conversion efficiency means is that you can have more power in less space. 'Space per watt' is just not a driver in the way that 'dollars per watt' is. If higher efficiency panels cost more per watt, there is relatively little that can offset this additional cost. So there is not a huge incentive for manufacturers to increase efficiency. The trend right now is the lowering of cost for modules that are basically staying at the same efficiency.
For many customers, there is little or no significant cost to space. If I'm a homeowner with 400 sq feet of roof available for solar panels, and I need 2 kW of power, it makes a small difference to me whether the 2kW of power takes up all 400 sq ft or only 300 sq feet. Maybe a little more in racking and labor costs for the less efficient panels, but that is a small and fungible part of the cost, in the low hundreds of dollars. It makes a
huge difference to me if the higher efficiency panels, the ones that allow me to use only 300 sq feet, cost $6000 instead of $4000. So higher efficiency better not cost significantly more in dollars per watt. But driving efficiency higher costs money in R&D, so it is hard to keep the dollars per watt competitive and drive efficiency higher at the same time.
Finally, just look at the industry. Sunpower, the highest efficiency guys, have a big market share, but so do First Solar, the lowest efficiency guys. The vast majority of the industry is somewhere in between efficiency-wise. Everyone's scared of Chinese manufacturers producing low cost, conventional silicon panels. If efficiency were most important, then everyone would be scared of Sunpower instead, but that's just not the case. Saying that efficiency is a big driver would be like saying that Cadillac's customers are determining major trends in the auto industry, instead of Toyota's.