Vietnam -
I was thinking this morning about some discussions I had with David Bowe, a fellow Vietnam Vet, about certain statistics from the war. I vaguely remember him saying 7? out of 9 GIs were "support" personnel like us. I found a few interesting things online just now. I'm copying several paragraphs from Michael Kelley's "Myths & Misconceptions: Vietnam War Folklore" here, and the second link has some interested stats as well.

Fact #1?
Most Vietnam Veterans Saw Combat:
Actually, the opposite is true; only a relatively small percentage were ever involved in combat. In fact, it is likely less than 30% of all who served there ever saw combat of any sort during their war.

Although the ratio of combat to support troops varied over time, as a general rule there where approximately 10 troops supporting every soldier carrying a rifle in the field. At the height of the war in 1969, there were roughly 540,000 troops in Vietnam. Of that total, only perhaps 60,000 were-rifle carrying, front-line soldiers. At any given point, perhaps less than 40,000 of that 60,000 were actually in the field, at risk and seeking contact with the enemy. Minor wounds, disease, R&R, leaves, training, administrative needs, rear assignments and legal proceedings kept perhaps 25% of an infantry company out of the line on a continual basis. During much of the war, Long Binh, regarded as the largest American facility, was staffed by over 100,000 US troops (that is roughly 20% of the entire US troop commitment at the height of our involvement!), of whom only a very small fraction (5-10%?) were assigned to a direct combat role. It was basically a self-contained city distinguished only from its stated-side counterparts by the lack of an underground sewage system and the miles of barbed wire that encircled it. And Long Binh was but one of hundreds of other permanent US military installations in Vietnam, several of which were similar in size and amenities. Tan Son Nhut Air Base, was the busiest airport in the world for much of the war; busier than either Chicago's O'Hare or New York's JFK. Other major bases of substantial size included Phu Bai, Bien Hoa, Pleiku, An Khe, Quang Tri, Cu Chi and the ports of Saigon, Da Nang and Cam Ranh Bay, to name a few.

At page 259 of Son Thang, An American War Crime, author Gary Solis points out that: "More than 448,000 marines served in Vietnam, although far fewer actually saw combat. One study asserts that no more than 71 percent of Vietnam veterans saw any combat at all. Combat itself may be defined on a sliding scale." Though life in the infantry was often intensely demanding both physically and emotionally, actual combat, fighting with the enemy, was actually relatively rare. In fact, on average most infantry companies made contact with the enemy no more than two or three times per month. For many, particularly those working in mountainous terrain, contact was even less frequent. Fatigue, boredom, physical discomfort and loneliness were the most common characteristics of infantry life; terror and death were only its occasional companions.

Fact #2?
Living Conditions For the Average US Soldier Were Very Difficult & Uncomfortable:
Again, though conditions varied over time and by occupation, the opposite was typically the case for the majority of those who served in-country. As a general statement, it is fair to say that between 1965 and 1967, living conditions were quite primitive. In those early years of US involvement, base sites were being chosen and developed by engineers, so tent living and Spartan lifestyles were
the rule. Once most major facilities were completed, the focus shifted to providing leisure time activities and comfort enhancements for the soldier.

For the most part, the 75-80% who never saw combat of any sort led lives comparable to, if not better than, stateside duty. In fact, it is little understood that there were a significant number of perks associated with combat zone duty not available to assignments elsewhere in the world.

A high percentage of Vietnam vets (perhaps 40%?) volunteered or even re-enlisted to remain in or return to the combat zone. Some did it over and over. Two, three and four tours were not uncommon and the author personally knows an Air Force NCO who spent six years in-country. Even a significant percentage of the infantry volunteered to extend their tours because they preferred combat life to stateside duty, though there were other reasons for extending as well, getting an "early-out" being one of them, and fear of returning being another. One added bonus was the additional $65 per month Combat Pay to which any enlisted person serving in the combat zone was entitled. Even though the majority were at much less risk than true combat soldiers, they received the same combat pay. As a general rule, advancement in rank was also much faster and much easier than in non-combat zone duty. Rules and regulations were relaxed in the combat zone. "Boot polishing," boot licking, physical training, marching drill and other military formalities were rarely enforced or as onerous as they were elsewhere. Of no small importance is the fact virtually everyone was armed and dangerous. As a result, otherwise contentious or obnoxious officers and NCOs were generally much better behaved in the combat zone. Those who risked men's lives needlessly or abused privilege of rank often found themselves at the wrong end of an M-16 or Fragmentation grenade. In fact, some 800 such "fraggings" were reported during the war, though it is likely the number was much higher. In some rare cases, rewards were offered informally for the dispatch of an officer or NCO perceived as particularly despicable. The highest rumored offering was for the life of General Melvin Zais, the commanding general of the Army's 101st Airborne Division responsible for ordering the costly and very controversial attack of Hamburger Hill in 1969. Recreational facilities were often elaborate and prolific: snack bars; steak houses, basketball courts; swimming pools, gyms; theaters, Clubs; R&R beach center (such as China Beach, Eagle Beach; Red Beach, Vung Tau, among others); BX facilities with heavily discounted items; PACEX mail-order services for all sorts of goods at heavy discount; access to extremely low cost alcoholic beverages at clubs and BXs; showers; walk-in medical and dental facilities; comfortable and sometimes air-conditioned quarters; ubiquitous U.S.O. entertainment (mostly Korean, Australian and US lounge lizard acts) and etc., etc. & etc. For those so inclined, access to the world of sexual pleasure was effortless, cheap and far removed from the normal constraints of family and neighborly influence. At the height of the war for example, over 56,000 registered prostitutes were working alongside US troops in Saigon alone. That is 56,000 not including the amateurs! For those so inclined, access to high quality, extremely low cost drugs (including alcohol) was abundant and of low risk. Dealing could be a very lucrative avocation; and even when discovered, punishments were generally lighter than elsewhere. Finally, for those possessed by even more relaxed moral standards, a strong bug of free enterprise and access to US supply depots, black market trading was a very busy and rewarding sideline. Some US personnel even sold stolen weapons on the black market, weapons that eventually ended-up in the hands of the enemy.

http://www.deanza.edu/faculty/swensson/essays_mikekelley_myths.html

http://www.uswings.com/about-us-wings/vietnam-war-facts/