Thursday 4 June 2009

How many dead dogs are there in the Harlem River?

Simple competition to win the bottle of champagne. Please provide details of your estimating basis and I will judge based on my primary research on Saturday.

Respond by email or blog comment.


1 comment:

John (TSPA) Weisz said...

Estimates on the total dog population of NYC (the 5 boroughs I assume) vary from .5 to 1.3 M. This is based on the fact that there are approximately 120K licensed dogs but only 10-20% of total dogs are estimated to be licensed. So we will take the midpoint of 900 K total dogs in NYC.

The Harlem River is bounded by two boroughs: The Bronx to the East and Manhattan to the West. These comprise approximately 13% and 7% of the total land area of NYC. Assuming a roughly even distribution of dogs throughout the five boroughs, we expect that there are 117 K and 63 K dogs in the Bronx and Manhattan respectively.

But given that the Bronx has about 33% greater proportion of its total land used for housing than does Manhattan, I will adjust the expected dog population by -/+ 20 K which makes the new estimates 137 K and 43 K dogs for the Bronx and Manhattan respectively.

But if your dog died, are you really going to drive all the way to the Harlem river to get rid of it? Only if you live close by I would argue. So I will make the further assumption that only 10% of people/dogs have convenient access to the river for disposal. So for all dogs currently alive in these two boroughs, we expect that 10% might possibly find their way into the Harlem river should they arrive at the end of their days. This means that about 18 K dogs might reasonably find their way into the river post mortem.

The average lifespan for a dog in the US and Europe is 12.8 yrs. or 4,672 days. Assuming the 18 K dogs have an even distribution of ages - from day of birth to day of death - on any given day, we expect that 3.8 of the 18 K dogs go to doggy heaven.

Now let us assume that if every one of those dogs made it to the Harlem river upon their deaths, they might stay there for 7 days before sinking, flowing out to sea, or being eaten by one of the many alligators that have been released in the NYC sewer system by children who have lost fingers when they got too big to handle.

This means that one might find 26.6 dogs in the river on any given day IF all of deceased canines made it into the river that week. But lets estimate that only 25% of New Yorkers are so heartless that they would dump Fido into the drink. that means that actually there are only 6.65 dead dogs along that stretch of river on any given day.

Given the fact that a dead dog tends to ride fairly low in the water (they have a large draft relative their total "height" in the water and a correspondingly small freeboard) AND given that the river is fairly wide, I estimate that a lone swimmer, with everything he has on his mind what with all the wretching and cramping he has going on, might be lucky to see one dead dog along his swim.

There is of course one flaw in this whole scenario (only one, you say?) and that is that I have avoided any dogs who might have either suffered death by misadventure in the river in any of the preceding 7 days, or perhaps who committed suicide jumping off the Hellgate bridge. But I am going to argue that those will be statistically insignificant numbers and in any event they should be included in the total dog mortality rates (life expectency actually) I quoted above.

Therefore, my estimate stands.

1 dog.