In this issue of Math in the News we look at the impact of a harsh winter on Florida's orange crop. In addition we look at an ongoing problem that orange production has had with a crop infestation. This provides opprotunities to apply percent change formulas to real-world data.

1. Math in the News
Issue 94
Winter’s Impact on Florida’s Orange Crop

2. Florida’s Orange Crop
For the past few years, Florida’s orange crop
had been struggling, due to a crop infestation.
This winter’s Polar Vortex effect has put more
pressure on this crop. In this issue we look at the
long-term prospects for Florida’s orange crop.

3. Florida’s Orange Crop
When it comes to orange production in the US,
Florida is king. This graph shows the overall US
production and Florida’s contribution to that
total. (Source: USDA.)

4. Florida’s Orange Crop
Over the past few years Florida’s production of
oranges has dropped. This has been due to an
infestation of the Asian psyllid, an insect that
transmits a bacterium that causes oranges to fall
from the tree long before they’re mature. It was
first detected in 2005.

5. Florida’s Orange Crop
Here is the data for
orange production in
Florida for the growing
seasons from 2001 to
2012. Input this data
into a spreadsheet.
Create a third column to
calculate the percent
change.
Year Tons (1000's)
2001-2002 727.6
2002-2003 718.1
2003-2004 679
2004-2005 641.4
2005-2006 576.4
2006-2007 554.4
2007-2008 538.9
2008-2009 530.9
2009-2010 517.1
2010-2011 503.6
2011-2012 495.1

6. Florida’s Orange Crop
Let’s measure the percentage drop in output
over the past few years. Use this formula for
percent increase and decrease.

7. Florida’s Orange Crop
Input a spreadsheet
formula for calculating
the percent change.
Use a variation of this
formula:
=(B2-B1)/B1
Format the output as
a percent.
Year
Tons
(1000's)
Percent
Change
2001-2002 727.6 --
2002-2003 718.1 -1.31%
2003-2004 679 -5.44%
2004-2005 641.4 -5.54%
2005-2006 576.4 -10.13%
2006-2007 554.4 -3.82%
2007-2008 538.9 -2.80%
2008-2009 530.9 -1.48%
2009-2010 517.1 -2.60%
2010-2011 503.6 -2.61%
2011-2012 495.1 -1.69%

8. Florida’s Orange Crop
Since its big drop in crop production in 2005,
there has been an average drop of 2.5% each
subsequent year.
Year
Tons
(1000's)
Percent
Change
2005-2006 576.4 -10.13%
2006-2007 554.4 -3.82%
2007-2008 538.9 -2.80%
2008-2009 530.9 -1.48%
2009-2010 517.1 -2.60%
2010-2011 503.6 -2.61%
2011-2012 495.1 -1.69%
Avg -
2.5%/yr

9. Florida’s Orange Crop
The change in output from 2005 to 2012 is the
product of each year’s net percentage.
A reasonable estimate is found using the
average percent change.

10. Florida’s Orange Crop
While crops have been in decline, the Winter of
the Polar Vortex has put the current season’s
harvest in further jeopardy.

11. Florida’s Orange Crop
The Florida
Department of Citrus—
http://fdocgrower.com—
estimates a 4% to 8%
drop in orange
production over the
next few years. Let’s
see what that could
look like. Let’s use our
previous spreadsheet
data.
Year
Tons
(1000's)
Percent
Change
2005-2006 576.4 -10.13%
2006-2007 554.4 -3.82%
2007-2008 538.9 -2.80%
2008-2009 530.9 -1.48%
2009-2010 517.1 -2.60%
2010-2011 503.6 -2.61%
2011-2012 495.1 -1.69%

12. Florida’s Orange Crop
Take the last data point and estimate the
output five years out for the two percentage
drops.

13. Florida’s Orange Crop
Use these expressions to find the potential
number of tons of oranges not produced over the
next five years.

14. Florida’s Orange Crop
• What is the potential loss in the orange crop
over the next five years?
• Estimate how many oranges this is.
• Estimate the volume this number of oranges
would take up.