Feeding America: The Extraordinary Increase in US Farm Productivity

A few nights ago I was re-reading a P.J. O’Rourke book on terribleness.  In the chapter on famine, everyone’s favorite bedtime reading subject, something he said struck me.  “In most of the world, food production has well outpaced the growth of population.  In the 1930s American wheat growers had an average yield of thirteen bushels per acre.  By 1970 the yield was thirty-one bushels.  In the same period the corn yield went from twenty-six bushels per acre to seventy-seven.”  This was unexpected. I have the picture in my mind of the differences between arithmetic and geometric progressions when it comes to comparing food production and population.  This is courtesy of Rev. Malthus, whose treatise was nicely summarized in the same book on terribleness in the chapter on overpopulation: “…there’s no end to the number of babies that can be made, but you can only plant so much wheat before you run the plow into the side of the house.

According to data from the fine folks at the USDA, the story here is rather interesting.  Yes, the wheat yield in the 1930s was in the low teens.  But what is surprising is that it had been there at least since the USDA began recording wheat crop yields in 1866!  In other words, the amount of wheat an acre of farmland produced showed no significant improvements for at least some seventy years, until the early 1930s.  Since then, however, it has increased at a roughly constant rate, reaching its all time high of 47.1 bushels per acre in 2013.  And it hasn’t settled at that yield; it continues to increase.

U.S. wheat crop yields, in bushels per acre.  1866-2014.

U.S. wheat crop yields, in bushels per acre. 1866-2014.

It should come as no great surprise, then, that corn yield numbers tell essentially the same story.  But I was surprised by the fact that the upturn in the yield happens at about the same date.  Corn production was a flat 25 bushels per acre for decades and started its way upward at about 1930.  For the curious, it peaked at 173.4 bushels per acre in 2014 and continues to climb as well.  That is a huge number.  A corn farmer in 1900 working hard to get his 28 bushels per acre never in his most fantastic dreams thought yields like this were possible.

U.S. corn crop yields, in bushels per acre. 1866-2014

U.S. corn crop yields, in bushels per acre. 1866-2014.

We can look at this another way, by plotting the corn yield against the wheat yield.  And what we see is that the relationship is well behaved.  When wheat yields increase, so do corn yields, though not necessarily in the same proportion.  After a point, every 10 bushels/acre growth in wheat equals about a 40 bushel/acre growth in corn.  This suggests there is more to the story — that there is some common factor that drives this effect.

The crop yields for U.S. corn plotted against the yields of U.S. wheat for the years 1866-2014.

The crop yields for U.S. corn plotted against the yields of U.S. wheat for the years 1866-2014.

And there is more to the story.  The USDA doesn’t just measure wheat and corn production.  They determine the yields for all of the field crops.  So that we can compare like things, first are the crop yields that are measured in bushels per acre: barley, corn, flaxseed, rye, sorghum, soybeans, and wheat.   Of those, only rye and sorghum yields look as though they have stopped increasing.  The rest show this continuously increasing trend over time, starting around the same year — 1930.

USDA crop yields (bushels/acre) for barley, corn, flaxseed, rye, sorghum, soybeans, and wheat.

USDA crop yields (bushels/acre) for barley, corn, flaxseed, rye, sorghum, soybeans, and wheat.

And then we have the crop yields that are measured by weight (pounds per acre).  These are: beans, cotton, hay, hops, peanuts, peppermint oil, rice, spearmint oil, sugarbeets, and tobacco.  These also show the same yield growth since about 1930 behavior.  Interestingly hay and tobacco yields seem to have joined rye and sorghum yields in leveling off (showing classic error function behavior).

USDA crop yields (pounds/acre) for beans, cotton, hay, hops, peanuts, peppermint oil, rice, spearmint oil, and tobacco.

USDA crop yields (pounds/acre) for beans, cotton, hay, hops, peanuts, peppermint oil, rice, spearmint oil, sugarbeets, and tobacco.

If it wasn’t clear before, it is now.  Sometime around the 1930s, something quite dramatic began to happen in field crop production.  An agricultural revolution of sorts.  And while the effect is present for all of them, it varies in its impact depending on the crop.  To show this, we normalize the yield rate by the average of the first few years in the dataset for a given crop.  This shows us how the yield rate has grown in time.  And we can compare them all if we plot them all with the same y-axis scale (conveniently done below).  So the biggest crops in terms of yield rate growth are:  corn (~7x), cotton (~6x), peanuts (~5.5x), rice (~7x), sorghum (4-6x).

Yield growth in US field crops.  Plotted is the multiplier in the yield rate since the start of data collection for the given field crop.

Yield growth in US field crops. Plotted is the multiplier in the yield rate since the start of data collection for the given field crop.

I find it interesting that the curves for soybeans and cotton begin to increase in 1920, which is a few years before the others.  Peanuts seem to be among the last to join the group as their yield didn’t start taking off until about 1950.  Did some experimentation take place with soybeans and cotton crops and then once successful transition to other crops such as wheat, corn, and then peanuts?  Soybeans became quite important in the US around 1910, so this is plausible.  Though I haven’t found anything to suggest this is what actually happened.

We do know that hybrid seed became all the rage starting around 1930.  Gregor Mendel demonstrated plant hybridization in the 1860s with peas, but it wasn’t until the 1930s when hybrid seed was able to produce a corn crop that was well suited to mechanical harvesting.  One report says: “The tractor, corn picker, and hybrid seed corn came together to raise labor and land productivity in corn production in the late 1930s.”  Tractor development (power takeoff, rubber tires) and sales really started to take off in the 1920s, which fits the timeline perfectly.  And I’ll bet that improved chemical fertilizers and pesticides factor in as well.

In any case, I should go back to the original statement where O’Rourke said food crop yield rates were increasing faster than the population.  In 1927 the world’s population is estimated to have been about 2 billion people.  This is convenient for our comparison as it about coincides with our 1930 start of this agricultural revolution.  Corn and wheat yields both doubled by about 1960, when the global population was about 3 billion (a 1.5x increase).  So far, so good.  And we reached about 7 billion people in 2012, an increase of a factor of 3.5 since 1930.  This about matches the rate of increase in wheat production.  But corn and rice have managed to stay ahead by a considerable margin, so O’Rourke is right and Reverend Malthus has been wrong.  At least, since this “revolution” started.

But these crop yield numbers aren’t global numbers, they’re for domestic production.  How do they compare against the growth in the U.S. population?  Quite favorably, it turns out.  In 1930 the U.S. population was about 123 million.  It grew by about 50 percent to about 180 million in 1960, which is in line with global population increase we just considered, where crop yields for corn and wheat doubled.  But in 2012 the U.S. population reached 313 million, a growth factor of only 2.5x over 1930.  The slowest of the food crop yields shown above have at least grown at the same pace as the domestic population.  But the major food crops like corn and rice are out in front by a mile, with their yields growing some 2.8 times faster than the growth in domestic population.

This is startling, but in a good way.  It is a win for science and innovation and demonstrates how humans can manipulate their situation to work to their advantage.  The primary food crop yields show no signs of leveling off.  It makes sense that they probably will at some point.  But for now it is nice to know that the Reverend Malthus is wrong.

Advertisements

Amherst Population Forecasts and Land Usage

Between 1960 and 1980 the town of Amherst, NH underwent tremendous population growth.  The US Census listed the town population at 2061 in the 1960 census and at 8243 in the one taken in 1980.  That is, in twenty years time the town’s population doubled twice.  This was a time when Amherst was transitioning from farms to the bedroom community as we know it today.  Some questions we might want to consider are what might the town’s population look like in the future and where will whatever growth we have take place in town.  The answers to these questions have a lot of impact on town planning needs, and frankly, these sorts of questions interest me in general.

In 1998 the town put together a master plan that, among other things, created a projection of the town’s population out to 2020.  As you can see from the graph below, the blue master plan projection numbers assumed that the growth rate of the last twenty years would continue into the next twenty years.   And maybe even increase a bit.  The forecast being created in 1998, the 2000 number matches well with the 2000 US Census, but overpredicts the 2010 numbers by about 1000.  Given the amount of developable land remaining in town and the zoning laws we have (e.g., 2 acre minimum lot sizes for new developments), the rest of the forecast looks suspiciously high.

Historic Amherst, NH population (red) and 1998 Master Plan projection (blue).

Historic Amherst, NH population (red) and 1998 Master Plan projection (blue).

In 2013 the State of New Hampshire’s Office of Energy and Planning put together municipal population forecasts for New Hampshire towns out to 2040.  Their projections are considerably more cautious than the ones the town created 15 years earlier, and suggest that we will slowly reach a peak population of about 12,000 people in about the next two decades.  In other words, population growth in Amherst is expected to continue, but not at rates even close to what the 1998 predictions suggested.

Historic Amherst, NH population (red) and 2013 state projection (yellow).

Historic Amherst, NH population (red) and 2013 state projection (yellow).

This seems to be reasonable.  Thanks to the fine folks at the Nashua Regional Planning Commission, we can take a look at the land usage in Amherst to get a feel for how much and where land is available in town for future growth.  In the plot below I have colored the various land usages in Amherst to correspond with how they are used.  So there are conservation land, lots currently used for housing, town property (schools, town offices, cemeteries, recreation land, etc.), commercial or industrial land, and wetlands and floodplains.  The uncolored lots are (or should be) available for development, although I can’t comment on how feasible they are.  It is an interesting map, and worth a close up look.  Perhaps 12,000 or so is the most people we can actually have in town.

Amherst, NH parcel map.  Colored lots are either developed, conservation land, town property, commercial/industrial, or floodplain/wetland.  Data courtesy of Nashua Regional Planning Commission.

Amherst, NH parcel map. Colored lots are either developed, conservation land, town property, commercial/industrial, or floodplain/wetland. Data courtesy of Nashua Regional Planning Commission.

The map above should be understood as a guide, as I can’t validate when the NRPC updates their parcel usage data.  But clearly the unused land that is available for potential development is in the minority of land in town, and that will be the limiting factor to the town’s future population.

Death and Burial Trends in Amherst

When it comes to understanding how we use our cemeteries in Amherst, something was still missing in my mind after going through the population growth in town, the annual burial numbers in our cemeteries, and also the cemetery lot sales numbers. To quickly review, since 1934, on average, we have a flat average of just 22 burials per year (+/- 6) in Amherst, NH cemeteries (see below).  The lot sales numbers indicate that we sell on average less than 8 cemetery lots per year (between 1971-2008), indicating that most of the burials are in lots that have been previously purchased (perpetual care lots).

Annual number of burials in Amherst, NH cemeteries. Data from Department of Public Works records.

Annual number of burials in Amherst, NH cemeteries. Data from Department of Public Works records. The red line shows the average value of 22.

This is rather surprising in light of the town’s population growth in that time. As per the US Census, we have gone from about 1000 people in Amherst to over 11,000 in that amount of time (see below).  So the conundrum is that even though there are 11 times more of us here now than there were 8 decades ago, the number interred in our cemeteries each year hasn’t changed.  At all.

US Census data for the town of Amherst, NH.

US Census data for the town of Amherst, NH.

This doesn’t make a whole lot of sense, but the numbers are all real.  Something to ponder while we press on.

One missing piece of this puzzle is the number of Amherst residents who die every year. Now you might guess that the number of residents who die and the number of people who are buried here would be basically the same.  This would make sense, but this would be wrong.  The number of resident deaths in Amherst is tabulated and reported every year in the annual town reports, which are available in the town library’s archive room, and that is where I obtained the numbers (graphed below). These are still remarkably small numbers, though they do show a slow growth trend, tripling in 8 decades.

Amherst Resident Deaths from 1934 to 2012, as recorded in Annual Town Reports.

Amherst Resident Deaths from 1934 to 2012, as recorded in Annual Town Reports. The blue line shows the running average.

So here is the conundrum now, since 1934 the population of Amherst has increased by a factor of 11, the number of annual resident deaths have gone up by a factor of 3, and despite those increases, the burial rate has not changed.

There’s a twist to this story, we just haven’t seen it yet.  It is difficult to plot resident deaths the same graph with the burial numbers for comparison, but we do need to compare them. So instead let’s look the ratio of burials to deaths.  This will be a much more useful graph.  Plotted here (see below) is our annual Amherst cemetery burials as a percentage of Amherst resident deaths each year. There is something quite surprising going on, do you see it?

Burials in Amherst, NH cemeteries as a percentage of Amherst resident deaths.  These numbers are skewed by the "Brought from away and buried in Amherst" burials.

Burials in Amherst, NH cemeteries as a percentage of Amherst resident deaths. The unlikely percentages are caused by the “brought from away and buried in Amherst” burials.

It turns out that it has been quite common for people to be “brought from away and buried in Amherst.” In some years those numbers have exceeded the numbers of Amherst residents who died. When that happens, we get some statistically very unlikely burial percentages, which you see above.  Now why people would be brought in for burial is a question for the historians.  But up until ten years ago or so, these “brought from away” numbers were in the town reports.  Whether or not this is still going on is an unanswered question at this point, and we have no information on the number “sent away” for burial.

One thing that is readily discernible here is that the percentage of dead which are buried is decreasing.  Let’s assume for a moment that the number of “brought from away” burials is currently the same as those who are sent away.  If this is true, the 2012 numbers show that about 50% of our residents who die are not buried.  Now if the number “brought from away” is greater than those sent away, as it must have been for many years, this fraction of residents not buried increases.  So what happens to the 50%+ who aren’t buried?

The answer, I believe, is cremation, an increasingly popular alternative to burial in this part of the country.  That explanation is consistent with the numbers that are reported here, and also with funeral homes reports in the area, which report that more than 60% are choosing cremation over burial.  The numbers from Amherst here are somewhat muddied by the fact that the head of DPW tells me that cremated remains are sometimes buried, requiring a lot and being recorded as a burial, so cremation rates in town are greater than what would be suggested here by burial numbers alone.

Now I think we have a reasonably complete picture of how we use our cemeteries in Amherst.  A useful thing to know for planning purposes would be the numbers of unsold and perpetual care (sold but unused) lots currently in town cemeteries.  We could use these, along with what we know from historic numbers, to forecast the number of years left before new cemetery space is required.

Amherst Cemetery Usage

With the cemeteries in Amherst making headlines in local news, I thought it was appropriate to obtain some numbers on the historic demand for the town’s cemetery land. The actual number of burials per year are only one facet of the issue, though. The other big aspect, which has not been a part of public discussion as I am aware of it, is the sale of burial plots. I am also working on those data in order to provide a more complete picture of our resource demands. That will have to wait, though. (Note:  Now complete.)

The town’s Department of Public Works has been very helpful with providing access to the town’s burial records (for which I am most appreciative), which go back to 1934 and are graphed below. These data conclude with the current year’s burial numbers, which, this being May, should be understood to be incomplete.

Annual number of burials in Amherst, NH cemeteries. Data from Department of Public Works records.

Annual number of burials in Amherst, NH cemeteries. Data from Department of Public Works records.

This graph nicely shows the fluctuations in the annual interment rates, and indicates that the data set is well represented by its mean value (red line). In order to make some other comparisons, however, we can determine the average number of burials per year, averaged over a decade, and replot. The graph below shows the average number of burials per year in the decade preceding the data point. So the 20.5 value in 1950 is the average number of burials from 1940-1949, and so on. The trend was clearly upward for the 2000-2010 decade, though it has fallen back to an average of 25 since 2010, as the graph above illustrates (not counting this year for obvious reasons).

Annualized mean burials in Amherst, NH cemeteries.

Annualized mean burials in Amherst, NH cemeteries.

In a previous post on the town’s population growth, the US Census was the primary source of data. There, the information is on the decade years and showed Amherst’s considerable growth. I have replotted these Amherst population data below, restricting the graph to just the years for which I have burial data. In the 60 years shown here, the population of the town increased from 1461 to 11,201 (by count of the US Census department).

US Census population data for Amherst during the burial data years.

US Census population data for Amherst during the burial data years.

The remarkable thing about this is that with the 766% increase in population of the town (2010 vs. 1950), the interment rate has remained largely flat. In other words, a shrinking percentage of the town’s population is being interred over this time, as shown graphically below. This should not be confused with our absolute burial space demand, which is clearly demonstrated by the first graph in this post.

Percentage of the population of Amherst buried, averaged for each decade.

Percentage of the population of Amherst buried, averaged for each decade.

This is a very surprising result. And probably not attributable to longevity, although life expectancy numbers in the US have increased (see below). I have no numbers on cremation or private cemetery usage, but those are likely possible factors in play.

Historic life expectancy in the United States.

Historic life expectancy in the United States.

What the population and interment numbers do tell us is that there are more of us in town every year, but a relatively fixed number of us are buried here annually.

Historic Population and Growth of Amherst and Neighboring Towns

The town of Amherst, NH has had much growth in the past few decades.  Some insight into that growth can be found by digging through town records as published in our annual Town Reports (available in the Reference Room in the town library).  Page 80 of the town report for the year 2000 provides data on the town’s annual population, as taken by Selectmen’s census, since 1960 and is shown here.  I find it interesting that we had only 2000 people in town in 1960.  These are very informative data, but are somewhat limited in value because in their short time scale.

Amherst, NH population as recorded in annual town reports.

Amherst, NH population as recorded in annual town reports.

The US Census records the decennial population, something they’ve been doing since 1790, which is plotted below for Amherst from 1910 until the most recent one in 2010.  Take note that the US Census data and the Selectmen’s Census from above do not generally agree in their absolute numbers, though they do follow the same trends during the years they overlap.  These US Census data, while they does not contain the fine level of detail that the Selectmen’s Census does, paint a much broader picture of the history and growth of the town and are useful for that analysis.

US Census data for the town of Amherst, NH.

US Census data for the town of Amherst, NH.

From is information, we can consider how and when our population has changed significantly.  For this, we will examine the percentage of change of the population of town from the previous decennial census (graph appears below).  These values paint a remarkable picture of the town’s growth.  The 1960 and 1970 decades (1970 and 1980 census values) show enormous growth in the town.  Between 1960 and 1970, the town’s population more than doubled (from 2061 to 4605).  And from 1970 to 1980 it almost doubled again (4605 to 8243).  After 1980, the growth rate plummeted and has remained relatively low.

The percentage change in the population of Amherst, NH from its previous decennial US Census.

The percentage change in the population of Amherst, NH from its previous decennial US Census.

To understand if this trend was broad or simply localized to Amherst, we can look at the same historic data for nearby towns.  The US Census populations of Bedford and Hollis are plotted together below with the Amherst data from above.  Note the large similar large population growths at approximately the same times.

US Census data for the towns of Amherst, Bedford, and Hollis, NH.

US Census data for the towns of Amherst, Bedford, and Hollis, NH.

We can also calculate the percent change for Bedford and Hollis and plot those data with our Amherst data from above.  The absolute values vary somewhat, but the data for the three towns all have in common several decades of large growth which peaked around the 1970 time period.

The percentage change in the population of Amherst, Bedford, and Hollis NH from their respective previous decennial US Census.

The percentage change in the population of Amherst, Bedford, and Hollis NH from their respective previous decennial US Census.

From these combined charts, we can conclude that the rapid population growth in the 1960s and 1970s was not localized to just Amherst.  Amherst and its neighboring towns experienced a population boom in the decades following the “baby boom” (1946-1964).