Let's count things

Arithmetic statistics is an area devoted to counting a wide range of objects of algebraic interest, such as polynomials, fields, and elliptic curves.  Fueled by the interplay of analysis and number theory, we'll count polynomials and number fields, which though basic objects of study in number theory, are quite difficult to actually count.  How often does a random polynomial fail to have full Galois group?  How many number fields are there?  We will address both of these questions today.