In 2007, all households in the United States earned roughly $7.723 trillion. One half, 49.98%, of all income in the US was earned by households with an income over $100,000, the top twenty percent. Over one quarter, 28.5%, of all income was earned by the top 8%, those households earning more than $150,000 a year.ne key measure is the real median level, meaning half of households have income above that level and half below, adjusted for inflation. According to the Federal Reserve, this measure was $51,939 in 2013, below the 1999 peak of around $57,000.
Edges. An edge is a line segment that joins two vertices. This tetrahedron has 6 edges. And this pentagon has 5 edges: An edge can also be the boundary of a shape. Such as the circumference of a circle.
The objects correspond to mathematical abstractions called vertices (also called nodes or points) and each of the related pairs of vertices is called an edge (also called an arc or line). Typically, a graph is depicted in diagrammatic form as a set of dots for the vertices, joined by lines or curves for the edges. Graphs are one of the objects of study in discrete mathematics.