Also, as to his business acumen and general economics skills.
"Our gross domestic product -- a sign of strength, right? But not for us. It was below zero. Who ever heard of this? It's never below zero."
(the same 2015 speech -- you really ought to look at it, you know.)
That's a claim that is, literally, impossible. And he wasn't even right in a charitable interpretation that he meant the *growth* in GDP, the "never below zero" claim is pretty obviously rubbish.
Or there's this, on how he assesses his wealth, from a 2007 lawsuit (that he lost):
" My net worth fluctuates, and it goes up and down with the markets and with attitudes and with feelings, even my own feelings, but I try... Yes, even my own feelings, as to where the world is, where the world is going, and that can change rapidly from day to day... I would say it's my general attitude at the time that the question may be asked. And as I say, it varies."
Or there's his brilliantly accurate estimates of the "beautiful, greatest, gorgeous" Border Wall cost:
"Let's say the wall will cost $4 billion, they say $10 billion. That means $4 billion if you know what you're doing." (September 14, 2015)
"The wall is gonna cost $6 or 7 billion." (November 8th, 2015)
"The wall's probably $8 billion dollars..." (February 9th, 2016).
"The wall gets built, it's gonna cost $10 billion to build the wall..."(February 29th, 2016).
"The wall's gonna cost $10 billion. Maybe 12..." (February 27th, 2016).
From which, I suppose, we can at least gather that we're glad Trump isn't a local builder come to give you a quote for your new patio. Especially as a professional construction expert apparently estimated a $25 billion+ cost for start-up (Washington Post, Feb 11th 2016) (and then double that within the next decade for maintenance, according to the Congressional Budget Office when auditing a similar project.)