Food for thought, I've seen mention that our consumption of sugar has been decreasing since 1999. Our waist line though has continued to increase. Some on this can be read and seen here in some charts.
Carbohydrate, Sugar, and Obesity in America
http://wholehealthsource.blogspot.com/2015/11/carbohydrate-sugar-and-obesity-in.html
While actual sugar consumption has been on the decline (as have carbohydrate intake as well), there's a difference between overall general population consumption being on the decline, and people, as a whole, actually lowing the intake to an amount conducive to losing weight.
For example, (with the exception of high performance athletes or the few that are fortunate enough to have great genetics), eating 400 grams of carbs (whether it be from starch or sugar) is going to make you gain weight. (or at the very least, stop you from losing weight).
Your chart was showing that carbohydrate intake has lowered from ~500g per day, down to around ~470g per day.
While that is a lowering of the overall number, it's not surprising that people are still getting fatter. 470g is still far too much. So the fact that people haven't started losing weight with a drop that minuscule doesn't negate the merits of carb reduction as the single best dietary approach to losing weight.
The food pyramid falsely suggests 300g...unfortunately, that's still too much.
If you're a sedentary adult, and you want to maintain your current weight, you should be targeting 150g of carbs per day or less.
Don't worry about calories (lower calorie consumption will happen by default simply by cutting out your starches and sugars)...
You don't need to buy into the "low fat" hysteria...eating fat won't make you fat.
You don't need to buy into the vegetarian/vegan agenda...eating meat won't make you fat.
Some years back, I was pretty overweight...at 6 feet 1, I was pushing 230lbs (and not lean).
I employed a strategy where I consumed less than 50g of carbs per day for 3 days, on the 4th day, I'd take it up to 125g of carbs...then repeat the cycle...all the while, making sure my protein intake was over 100g per day. I went from 230 down to 170 in under a years time. My triglycerides went from 110 down to 40, my cholesterol dropped from 210 down to 160. (final number was 102 ldl/58 hdl...which is considered great).
During that time period, i wasn't working out...and I wasn't paying any attention to fat content, calories, cholesterol content, etc... protein and carbs where the only numbers I was tracking.
The last 2-3 years for me have been focused on weight training and packing on lean muscle mass, so these days, I'm doing 200g of carbs on training days (most of those being pre-workout) and 150g on off days. My protein intake is around 175-200g per day. My BF percentage stays somewhere in the 11-14% window. (Depending on the time of year...I keep a little more weight on in the winter/fall since I'm not hanging out by the pool shirtless during that time of year)