I will note that I went through the mental exercise of cars in a much simpler (and I would say better) way: I took the number of cars in the US (300 million was my guess for this, which is actually fairly close to the actual figure of 254 million claimed by the same article that you referenced) and guessed about how long cars typically ended up lasting before they went away (my estimate range was 10-30 years on average). To have 300 million cars, that would suggest that we would have to purchase new cars at a sufficiently high rate to maintain that number of vehicles given that lifespan. So that gave me a range of 10-30 million cars purchased per year.
The number of 5 million cars per year absolutely floored me, because that actually would fail my sanity check—to get 300 million cars, that would mean that cars would have to last an average of 60 years before being replaced (and in actuality would indicate a replacement rate of 250M/5M = 50 years, ish).
The actual cause of this is that car sales have PLUMMETED in recent times. In 1990, the median age of a vehicle was 6.5 years; in 2007, it was 9.4 years, and in 2011, it was 10.8 years—meaning that in between 2007 and 2011, the median car had increased in age by 1.4 years in a mere 4 years.
I will note that this sort of calculation was taught to me all the way back in elementary school as a sort of “mathemagic”—using math to get good results with very little knowledge.
But it strikes me that you are perhaps trying too hard in some of your calculations. Oftentimes it pays to be lazy in such things, because you can easily overcompensate.
I will note that I went through the mental exercise of cars in a much simpler (and I would say better) way: I took the number of cars in the US (300 million was my guess for this, which is actually fairly close to the actual figure of 254 million claimed by the same article that you referenced) and guessed about how long cars typically ended up lasting before they went away (my estimate range was 10-30 years on average). To have 300 million cars, that would suggest that we would have to purchase new cars at a sufficiently high rate to maintain that number of vehicles given that lifespan. So that gave me a range of 10-30 million cars purchased per year.
The number of 5 million cars per year absolutely floored me, because that actually would fail my sanity check—to get 300 million cars, that would mean that cars would have to last an average of 60 years before being replaced (and in actuality would indicate a replacement rate of 250M/5M = 50 years, ish).
The actual cause of this is that car sales have PLUMMETED in recent times. In 1990, the median age of a vehicle was 6.5 years; in 2007, it was 9.4 years, and in 2011, it was 10.8 years—meaning that in between 2007 and 2011, the median car had increased in age by 1.4 years in a mere 4 years.
I will note that this sort of calculation was taught to me all the way back in elementary school as a sort of “mathemagic”—using math to get good results with very little knowledge.
But it strikes me that you are perhaps trying too hard in some of your calculations. Oftentimes it pays to be lazy in such things, because you can easily overcompensate.