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<div class=Section1>
<p class=MsoNormal><span style='color:#1F497D'>After more investigation, it
appears that the 3-year estimates are, in fact, controlled to a moving average
centered on the middle year. But you have to use the right 3-year estimates.
When we did this with the most recent estimates (which now go to 2008), the
three-year average centered on 2006 did NOT match, but when we looked at the
historical release of 2007 estimates, and used those to calculate an 3-year
average, the result DID match the 3-year ACS total.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>I still find it confusing that the
characteristics are NOT averaged, but the totals are?????<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='color:#1F497D'>Frank<o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
ctpp-news-bounces@chrispy.net [mailto:ctpp-news-bounces@chrispy.net] <b>On
Behalf Of </b>Michael Cline<br>
<b>Sent:</b> Tuesday, April 21, 2009 8:25 AM<br>
<b>To:</b> ctpp-news@chrispy.net<br>
<b>Subject:</b> RE: [CTPP] Comparison of ACS 1-year, ACS 3-year & Annual
Estimates <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='color:#1F497D'>Someone from the ACS discussed
this in January at TRB (at the Census subcommittee meeting).
Unfortunately, I cannot find my notes, but I seem to recall that the 3-year
estimates use a middle population estimate (i.e. 2006). <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>Michael E.
Cline</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif";
color:#1F497D'> <br>
</span><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>Research
Associate</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif";
color:#1F497D'> <br>
</span><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>Institute
for Demographic & Socioeconomic Research</span><span style='font-size:12.0pt;
font-family:"Times New Roman","serif";color:#1F497D'> <br>
</span><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>The
University of Texas at San Antonio</span><span style='font-size:12.0pt;
font-family:"Times New Roman","serif";color:#1F497D'> <br>
</span><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>1
UTSA Circle</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif";
color:#1F497D'> <br>
</span><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>JPL
4.03.18A<br>
San Antonio, TX 78249-0704</span><span style='font-size:12.0pt;font-family:
"Times New Roman","serif";color:#1F497D'> <br>
</span><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'>(210)458-6537
f(210)458-6541</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif";
color:#1F497D'> <br>
<a href="mailto:michael.cline@utsa.edu"><span style='font-size:10.0pt;
font-family:"Futura Lt BT"'>michael.cline@utsa.edu</span></a> <br>
</span><i><span style='font-size:10.0pt;font-family:"Futura Lt BT";color:blue'><a
href="http://idser.utsa.edu/">http://idser.utsa.edu</a></span></i><span
style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'> </span><span
style='font-size:10.0pt;font-family:"Futura Lt BT";color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif";color:#1F497D'> </span><span
style='color:#1F497D'> <o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> ctpp-news-bounces@chrispy.net
[mailto:ctpp-news-bounces@chrispy.net] <b>On Behalf Of </b>Frank Lenk<br>
<b>Sent:</b> Monday, April 20, 2009 11:26 PM<br>
<b>To:</b> ctpp-news@chrispy.net<br>
<b>Subject:</b> [CTPP] Comparison of ACS 1-year, ACS 3-year & Annual
Estimates <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='color:#1F497D'>The attached spreadsheet was
prepared by my staff, showing the comparison in total county-level population
between the 2007 ACS 1-year estimates, the 2007 ACS 3-year estimates and the
Census Bureau’s July 1, 2007 population estimates by county. The
latter are supposed to be the official population estimates to which ACS is
controlled. And, based on the attached spreadsheet, this appears to be
true for (most) counties in the 1-year estimates. But the total
population in the 3-year ACS estimates is systematically biased downwards from
the total population in the 1-year ACS estimates and/or the official
estimates. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Does anyone have a good idea
why?<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>There is some vague language
about differences in weighting in the Census Bureau’s documentation, but
I can’t find a satisfying explanation. I do notice that the faster a
county is growing the bigger the discrepancy between the 3-year and 1-year
estimates of total population. This suggests that the 3-year estimates are
being controlled to an average of the 3 years of official total population
estimates (2005, 2006 and 2007). But my understanding is that the3- year
ACS estimates are not averaged. Instead, they a represent a single sample
taken over a 3-year period. My expectation, then, is that this sample
would be expanded to the same population as the 1-year estimates – The
3-year and 1-year estimates are, after all, identified by the same year (2007)
while a 3-year estimate based on a 3-year moving average would be closer to
2006’s 1-year estimate. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Any help in clarifying this
issue would be greatly appreciated.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Sincerely,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Frank<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='color:#1F497D'>Frank Lenk<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Director of Research Services<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Mid-America Regional Council<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>600 Broadway, Suite 200<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Kansas City, MO 64105<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><a href="http://www.marc.org">www.marc.org</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>816.474.4240<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><a href="mailto:flenk@marc.org">flenk@marc.org</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>816.701.8237<o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
</div>
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