Hello,
I am doing a small research about the car rental market.
Does anyone has an idea what is the average percentage of cars in the rental companies' fleets that are not in use? In other words, do the rental companies have too many cars and don't use some percentage of those they purchased?
If anyone have the answer or can turn me to a resource where I can find this info I would be thankful.
Thanks,
Erez.

It doesn't really work like that. Some vehilcles are rented more frequently than others, while others are rented out less frequently. Sometimes you will go to a car rental lot and there will be vehicles as far as the eye can see. Other times, you may be able to count on one hand the number of vehicles that are available. There are high and low demand periods, but all the vehicles end up on rent some portion of the time.

For example, Hertz in the Los Angeles area has been sold out the past two weekends at many locations. We're talking completely sold out at Santa Monica, Venice, around LAX and even LAX airport itself. You go on their website to reserve and there is zero availability. There might be a few scattered vehicles around, but they are not taking any reservations because they are at or close to 100% utilization.

The rental companies have gotten better at "right sizing" their fleets in recent years based on expected demand patterns. They aren't perfect by a long shot, but for the most part, they do a decent job. In short, they use all their cars, it's just that the utilization may vary depending on location, model, demand, competition, etc.

As AutoSlash said, there's usually a buffer, albeit a very small one. Some customers don't show up, which releases spare capacity. Other times, cars randomly break down, even on a sold out day in a market experiencing their peak season. In a few cases, an elite status customer reserves at the last minute, on a contract that allows guaranteed availability with a certain number of hours advance notice.

So when the rental company stops taking reservations, there may still be a very small number of "extra" cars left. But not enough to write a research paper on, if that's what you were hoping for.

Think about it this way. Imagine you're having a birthday party. You expect 25 guests. You will probably order a little extra food, maybe for 27 people. Too much more, expensive food gets wasted. Where it becomes a problem is when you try to be clever and assume 30% will no show, so you order 30% less food, to save money. Then, big shock, everybody actually shows up, meaning some people won't get to eat. Judging by more frequent sell-outs in large markets, I wouldn't be surprised if rental companies are increasingly trying this tactic.

AutoSlash and Auto Enthusiast thanks a lot for your detailed answer which helps me a lot.This "research" is done in order to examine a business collaboration. I read that rental companies are looking for new growth directions and we try to understand what can work out in this context. Is there any chance that one of you could dedicate 5 minutes for me for a Skype call? If you are not too busy for that, my nickname is erezeven. I would be thankful for that. Thanks.