Trump's Wall: Expensive and Least Effective Protection

We already have a wall. It gets climbed over. Trump's will too. But, more than that, Trump's Border Wall Is An Example of Bad Leadership; the cost to build Trump's wall, taking down what is existing, I assume, and building a new cement wall or something similar, is mind-boggling. Like his recent ban on Muslims, which he did not carefully and critically examine prior to implementing, a wall will fail to do what is expected, have unintended consequences—if nothing else, as a result of his proposed 20% tax on Mexican imports—and "is the most expensive and least effective way to secure our border."