A couple of months back I had one of "those" discussions at an Indian restaurant where I was trying to compare the productivity of dairy cows versus people to make some point that now completely eludes me. At the time I couldn't work out the numbers but the idea stuck with me so I thought it was high time I sat down and worked it out.

My proposed equation goes like this:

Your annual income / the price of milk solids / the amount of milk solids a cow produces in a year = number of cows you are worth

According to "Go Dairy" the average New Zealand dairy cow products 3,567 litres of milk a year: http://www.godairy.co.nz/page/pageid/2145843551 - Apparently it takes 12 litres of milk to produce one kilogram of milk solids: http://www.oilyrag.co.nz/beverages.htm - That means the average New Zealand dairy cow produces 297 kilograms of milk solids per year.

Fonterra is forecasting it will pay NZ$4.55 per kilogram of milk solids in 2010 (down from $5.20 in the previous season - http://www.nzherald.co.nz/business/news ... d=10588787 ). Which means the equations goes something like this:

Your annual income / $4.55 / 297kg

For example; if we take an income of $50,000 we get:

$50,000 / $4.55 / 297kg = 37 cows

At this (last?) seasons prices: $50,000 / $5.20 / 297kg = 32 cows

Heh heh... cows...