I've heard it quoted that 3-4 times more bombs were dropped during the American involvement in Vietnam than in WWII (6-8 million metric tons versus 2 million [though the USSBS says 2.7 million]). Based on my admittedly limited knowledge, this seems strange- from what I've read, the Vietnam-era Air Force and Navy were heavily hamstrung both by government micromanagement and the pressure of foreign and domestic popular opinion in terms of their ability to strike targets. Olof Palme's denunciation of Linebacker II as a crime against humanity comes to mind, despite those attacks being far less damaging than any number of WWII strategic bombing raids. In addition, the numbers of aircraft involved were far lower, on the scale of several hundred versus many thousands of aircraft in action during the world war.
The factors that I can think of that would have influenced the numbers upward would be the relative bomb loads of the aircraft, the greater length of the conflict, and the lesser concern over/casualties from air defense.
Is this all, or is there some part of the equation that I'm missing here? Also, and this is probably more pertinent- why is my perception of the relative sizes of the bombing campaigns divergent from reality? I'm sure millions of tons of those bombs were dropped in Laos and Cambodia, so is part of it just a U.S. attempt to cover up or downplay aspects of the air war in order to influence public views of the war?
They calculate tonnage of bombs in equivalent amount of TNT to produce a given amount of destruction, not the actual physical weight of a bomb dropped. So as munitions tech advanced they were able to put stronger explosives into bombs of a given size. Additionally they made larger aircraft, in particular the B-52 which was put into use in 1955 after WWII that could drop more bombs. Those two things means the tonnage of bombs used go up dramatically.
Also, while the Vietnamese had significant anti-air power in the northern half of the nation, the southern section which most of the combat took place in had much less available. We could also park aircraft carriers nearby, and build airbases all around, and fly missions at any time with relative ease, compared to the difficulty of contending with the Luftwaffe and Japanese air forces (until they began to crumble near the very end of WWII).