Will Trump's Troops on the Border Really Help?

Trump has announced and obtained DOD approval to put 4,000 National Guard Troops at the Mexican Border to reduce the number of illegal immigrants entering the US.  Not that he has ever used data or logic to make such decisions, so I thought I would try to put his decision up against some actual data!

First, I downloaded aprehensions for the Southwest Region from 2000 to 2018 FY to date ,by month,  from US Customs and Border Protection as well as annual data from 1960 to 2017.

For context, take a look at the annual data in simple graph form below:

The first thing to notice is that aprehensions had been steadily increasing from 1960 - 2000 after which a rapid decline began.  For context, in 1979, Reagan campaigned on creating a North American Trade Agreement and through the 1980's negotiations began.  Clinton finally signed the agreement in 1993 and it was put into action in 1994.  The Agreement stated most tariffs were to be eliminated within 10 years. The NAFTA implementation might have been a contributor to the decline beginning 2001, which, by the way, was the first year of the Bush Presidency.

To get a better handle on the compound annual growth rate of apprehensions and the stability, the graphs below analyze the periods prior and post 2000:

From 1974 to 2000, the growth was quite steady at 3.7%, compounded annually, with 1986 showing up as a uniquely different year being above the Upper Control Limit (middle of negotiations?).  From 2001 to 2017 the decline was -8.8% at an undisturbed rate.  It was during these years that both Bush and Obama, sent troops to the border to help with apprehensions, which were already in steady decline.

Using monthly apprehension data beginning in 2000, lets now look at previous troop deployments to assess their impact, remembering the decline of -8.8% indicated a steady, stable decline.

Bush sent 6,000 troops to the border in 2006, which lasted two years, at a cost of $1,200 Mil.  Apprehensions connected with this deployment were only 176,000 of the 2,030,000  two year total or 9%. Clearly there were no INCREASES in monthly apprehensions during this deployment as seen in the graph above.  (The annual seasonal pattern spikes in March and bottoms in December)

The first graph above compares the two years prior to Bush's deployment to the two years of the deployment.  The conclusion would be that apprehensions dropped by 38% due to the deployment.  In the second graph, in the two years after the deployment, apprehensions dropped another 21.5%.  These last 3 graphs would cause me conclude that there was no impact in apprehensions from Bush's deployment. The $1,200Mil spent did NOT produce any "net extra apprehensions"

Below, you will see a similar analysis of the troop deployment done by Obama in 2010 which lasted only one year at a cost of $110 Mil for 1,200 troops.

Again, Obama claimed 18,000 troop based apprehensions during 2010 of the total 447,731 or 4%.  During 2010, average apprehensions dropped by 22.5% as compared to the 2009 and in 2011 apprehensions remained the same as 2010.  So again, troops at the border did not create any additional apprehensions.

So now Trump is sending 4,000 troops to the border as a "hair on fire" reaction to a lack of his wall being funded, but does the data support his reaction?

 Average apprehensions during Trump's administration are 34.7% lower than the average of the Obama years.  You can see that March 2018 is a large rise, but not outside the the Upper Control Limit.

So, troops at the border probably will not make any difference in apprehensions at the border.  Maybe we should just treat this deployment as Trump's Military Parade!  One final thought: Could the rise in apprehensions during Trump's administration be caused by Trump declaring the end of NAFTA, mirroring the rise prior to the implementation of NAFTA we see in the annual data??