Even if it is by design, it does not explain why the numbers are going down. Even if tobacco would take 50% of all deaths and we have a lottery that takes out another 25%, the number can still grow. So unless you show me what the percentage of tobacco death are during the years they are talking about, it means nothing in this context. It does not explain why the numbers are starting to get lower. It explains why they are high as they are, but not the change, unless you have numbers that back it up.
You should also look to other countries and see what the reason might be.
You want clarity behind the numbers when the numbers quite literally slipped fractions of a percent across the aggregate. I'm not going to even try and distill that level of needle-in-a-haystack analysis when statistics can be mutilated to the point of being utterly worthless. Suicides and depression is up. Economy isn't exactly wonderful. Opiate addiction is on a rampage, along with a socialized healthcare system that is creating heroin addicts as a side-effect. A super-sized obese society. Take your pick as to why the numbers are "going down".
And the key number that has been held down is the population number. Without death by design, we would be facing a whole new wealth of issues related to resource management. Population control is a key component of resource management.
Tobacco was but one example I provided that kills hundreds of thousands of Americans every year, approved by the very Government that not only benefits from taxation, but also meets the obligation of resource management and creates massive profits treating related illnesses before a premature death. It's a win-win-win.