How do I create a variable storing the average change in population growth per country across a 10 year period?

[Zach Goldberg]

As the title suggests, I'm working with census data. I'd like to generate a variable that stores the average annual rate of change in population growth across a 10 year period.
My variables are as follows: 'YEAR' = 2005-2015; 'country' = 87 countries of interest; 'TOTPP' = estimate of total population. Can anyone help me out with the command for this? Thanks in advance!

[Zach Goldberg]

Nobody? : (

[William Lisowski]

The most common reason questions go unanswered is that the question is unclear. That, for me, is certainly the case with your question.

Please review the Statalist FAQ linked to from the top of the page, as well as from the Advice on Posting link on the page you used to create your post, looking especially at sections 9-12 on how to best pose your question. It would be particularly helpful to post a small hand-made example, with your 11 years of data for just two or three countries, showing the data and the results you expect to calculate from that data. In particular, please read FAQ #12 and use dataex to post your sample data to Statalist.

With sample data to play with and a clear explanation of what the expected result is, perhaps someone can help. How do you define "population growth" from population? How to do you define the "rate of change in population growth"? How do you average this - across the 11 years separately for each country, or across all countries separately for each year, or across all countries and all years?

The more you help others understand your problem, the more likely others are to be able to help you solve your problem.

[Zach Goldberg]

Hey William,

Thanks for clearing that up for me. To begin anew, these are the variables I'm working with:

* Example generated by -dataex-. To install: ssc install dataex
clear
input long country double(YEAR TOTPP)
269 2005 296139635
269 2006 298860519
269 2007 301655953
269 2008 304473143
269 2009 307231961
269 2010 309876170
269 2011 312390368
269 2012 314799465
269 2013 317135919
269 2014 319448634
269 2015 321773631
270 2005    107768
270 2006    107477
270 2007    107166
270 2008    106859
270 2009    106590
270 2010    106382
270 2011    106244
270 2012    106174
270 2013    106166
270 2014    106208
270 2015    106291
200 2005   3761143
200 2006   3749653
200 2007   3738549
200 2008   3728126
200 2009   3718473
200 2010   3709671
200 2011   3701997
200 2012   3695674
200 2013   3690591
200 2014   3686517
200 2015   3683238
 94 2005     56953
 94 2006     56958
 94 2007     56896
 94 2008     56788
 94 2009     56663
 94 2010     56546
 94 2011     56441
 94 2012     56344
 94 2013     56265
 94 2014     56211
 94 2015     56186
 76 2005     48337
 76 2006     48505
 76 2007     48599
 76 2008     48629
 76 2009     48613
 76 2010     48567
 76 2011     48492
 76 2012     48393
 76 2013     48292
 76 2014     48221
 76 2015     48199
 39 2005  32253092
 39 2006  32610984
 39 2007  32985806
 39 2008  33369898
 39 2009  33752618
 39 2010  34126240
 39 2011  34499905
 39 2012  34868151
 39 2013  35230612
 39 2014  35587793
 39 2015  35939927
 22 2005     65124
 22 2006     65064
 22 2007     64891
 22 2008     64627
 22 2009     64306
 22 2010     63954
 22 2011     63578
 22 2012     63179
 22 2013     62773
 22 2014     62376
 22 2015     62004
 24 2005    329088
 24 2006    335622
 24 2007    342049
 24 2008    348340
 24 2009    354492
 24 2010    360498
 24 2011    366711
 24 2012    372388
 24 2013    377841
 24 2014    383054
 24 2015    388019
 57 2005  11292078
 57 2006  11301100
 57 2007  11301674
 57 2008  11296355
 57 2009  11288826
 57 2010  11281768
 57 2011  11323570
 57 2012  11342631
 57 2013  11362505
 57 2014  11379111
 57 2015  11389562
106 2005   9260879
end
label values country country
label def country 22 "BER", modify
label def country 24 "BHM", modify
label def country 39 "CAN", modify
label def country 57 "CUB", modify
label def country 76 "FAE", modify
label def country 94 "GLD", modify
label def country 106 "HAI", modify
label def country 200 "PTR", modify
label def country 269 "USA", modify
label def country 270 "USV", modify

As mentioned earlier, I'd like to create a variable that stores the average population growth rate per country across 2005-2015. By 'average population growth rate', I mean the following:

USA population in 2015 - USA population in 2014 = annual population growth

+

USA population in 2014 - USA population in 2013 = annual population growth

And so on and so forth (for every country). Then I mean to sum each annual population growth and divide by the number of years (10) to obtain the average. I'm just not sure what the syntax would be for creating a variable that generates and stores all of this information. Help on this would be much appreciated. Let me know if anything is still unclear. Thanks again!

[German Rodriguez]

If you want absolute changes, the following will do

. bysort country (YEAR): gen change = TOTPP[_n] - TOTPP[_n-1]
(10 missing values generated)

. list in 1/5

     +---------------------------------+
     | country   YEAR   TOTPP   change |
     |---------------------------------|
  1. |     BER   2005   65124        . |
  2. |     BER   2006   65064      -60 |
  3. |     BER   2007   64891     -173 |
  4. |     BER   2008   64627     -264 |
  5. |     BER   2009   64306     -321 |
     +---------------------------------+

The code sorts by country and makes sure within country the data are sorted by year. Each country will have the first observation missing. For BER we don't know the change from 2004 to 2005. Obviously this country is losing population.

In demography interest often centers in relative change. For example BER is loosing population at an average rate of half a percent per year, which you can obtain as log(62004/65124)/10 = -0.0049. This may be more meaningful than an average absolute change, and can be calculated as

. bysort country (YEAR): gen rate = log(TOTPP[_N]/TOTPP[1])/(YEAR[_N]-YEAR[1])
(1 missing value generated)

. egen tag = tag(country)

. list country rate if tag

     +---------------------+
     | country        rate |
     |---------------------|
  1. |     BER   -.0049094 |
 12. |     BHM    .0164729 |
 23. |     CAN    .0108235 |
 34. |     CUB    .0008596 |
 45. |     FAE   -.0002859 |
     |---------------------|
 56. |     GLD   -.0013559 |
 67. |     HAI           . |
 68. |     PTR   -.0020931 |
 79. |     USA    .0083017 |
 90. |     USV     -.00138 |
     +---------------------+

We get a missing value for HAI because it has only one observation. You may find a handout on growth rates here