I'm only playing devil's advocate here, but when the majority of the 6% are already approaching life's exit, they're probably not boosting the economy much to begin with by way of consumer spending. Most old folks are lucky to get by at all.
That is not intended to be a pro/con "kill the old folks" thing... Just saying that if the death toll gets that high, it may not have the impact you think it would. Now if that 6% was concentrated at mid-lifers who are in the peak of their earning and spending years, yes, that would be a problem.
Who would they market the clapper to? Who will buy Depends? Who will buy "pocket catheters"? Who will buy up the large supply of white walking shoes with velcro straps?