In examining data, we can see telling relationships about agriculture. Here these relationships – and ways of visualizing them – are discussed.

Data by farm size

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Yesterday I wrote a post about pork agriculture in the United States. In this post, I made a graph from the following data, which is from the 2012 US Census of Agriculture:

Hogs/Pigs on Farm	Farms	Hogs/Pigs
1 - 24	41,688	244,250
25 - 49	3,435	116,808
50 - 99	2,161	146,967
100 - 199	1,469	201,460
200 - 499	2,115	683,977
500 - 999	1,977	1,384,921
1000 - 1999	2,677	3,662,168
2000 - 4999	4,718	14,867,199
5000+	3006	44,719,035

This data can be used to make a bar chart showing how many hogs and pigs are on large farms. Below is the graph I used in yesterday's post.

This graph is informative, but doesn't reflect all the interesting things in the above data. For instance, seeing this graph alone might lead you to an assumption that most farms are factory farms, but that's not true. Let's take a look at a graph of the number of farms by farm size.

Trends can help explain perceptual disparity between facts and anecdotes.

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This trend is pretty surprising, but also may explain discrepancies that I have personally encountered. While we know that 96% of hogs and pigs are on factory farms, it can be hard to convince people that this is true. On several occasions when I have discussed pork agriculture with people, it is brought up that they know a friend or a family member who has worked on a farm where things aren't nearly as bad as "the other farms."

Knowing that most farms are small while most hogs and pigs are on factory farms provides some explanation for this: while you are more likely to have seen or heard about a small farm, the pork on your plate is extremely likely to have come from a factory farm. Notably, the disparity between farms people have encountered and the prevalence of factory farms is exacerbated when you consider that people who have the luxury of leisurely discussing livestock populations are less likely to be around factory farms, since hog factory farms are about nine times more likely to exist in areas affected by poverty.

Combining graphs

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It would be great to show all of this information in one simple graph, but to do so there should be a common metric that works to both numbers. While the number of total farms is in the ten thousands and the number of total pigs and hogs is in the ten millions, we can examine both of these quantities by farm size as a percentage of the total. Using the above data, we can make this conversion.

Hogs/Pigs on Farm	Percentage of total farms	Percentage of total Hogs/Pigs
1 - 24	65.914050	0.3699256
25 - 49	5.431174	0.1769100
50 - 99	3.416817	0.2225869
100 - 199	2.322677	0.3051186
200 - 499	3.344085	1.0359084
500 - 999	3.125889	2.0975139
1000 - 1999	4.232679	5.5464884
2000 - 4999	7.459760	22.5169210
5000+	4.752870	67.7286271

In order to graph this data, a bar plot with two variables does the trick.

This graph illustrates disparity farms and livestock that helps to explain the anecdotes I personally have encountered. The drawback of this representation is that specific numbers are not available, and a viewer would not be able to tell that there are about 42 thousand farms with 1 - 24 pigs and hogs, or that 45 million pigs and hogs are on farms with over 5000 of the same species.

I hope this walkthrough has been informative and interesting! All code used to generate these charts is on github.

Until next time

^{This post is CC BY 4.0}