My first step in analyzing
the postage data was to create a table and corresponding charts in Excel. I was also aware that more recent postage
data was available so I looked up changes to the postage rate at http://www.akdart.com/postrate.html
from this information I created two charts and developed trend lines in Excel
utilizing the trend line function. I
chose to utilize exponential trend lines because these resulted in the most
accurate models. Each of the 2 data sets
resulted in slightly different equations.
The first dataset from 1933 to 1996
resulted in the equation y = 1E250x76.173 where y is the dependant variable,
the amount of the postage, and x is the independent variable, the year. The next dataset from 1933 to 2006 resulted in the equation y =
3E254x77.242 where again y represents the postage in cents and x represents
the year.
As you can see from the
predicted values in the table utilizing
the predicated values from the different data sets results in slightly but very
close predications for when the cost of 1^{st} class postage reaches 64
cents, 1 dollar, and the next 3 cent increase.
A summary of my findings and predications based on these two models is
below.

Prediction 1 (based on
dataset from 1933 to 1996) 
Predication 2 (based on
dataset from 1933 to 2006) 
64 cents 
Late 2021 
Early 2022 
1.00 
2033 
2034 
Next 3 cent increase 
2009 
2009 
Equation 
y = 1E250x76.173 
y = 3E254x77.242 
Error statistic 
26.3 
26.0 
I have also calculated the
error statistic between the predicted value and the actual value for all the
known years. As you can see the
statistic is more accurate for the second prediction equation and I would
therefore utilize this equation in any further predictions.
For a look at the entire
excel file click here.