\begin{tikzpicture}[
  arrow/.style = {
    draw,
    -latex,
  },
  plain/.style = {
    draw=none,
  }
]
  \coordinate(o) at (0,0);
  \coordinate(y) at (0,4);
  \coordinate(x) at (6,0);

  \coordinate(c1) at (0.5,0.5);
  \coordinate(c2) at (2.5,2.5);
  \coordinate(c3) at (3.5,2.5);
  \coordinate(c4) at (5.5,0.5);

  \path[arrow]
    (o) --
      node[plain, below, pos=0.9]{time}
    (x);
  \path[arrow]
    (o) --
      node[plain, pos=0.2, left]{%
        \begin{tabular}{c}
          thin\\
          clients
        \end{tabular}
      }
      node[plain, pos=0.8, left]{%
        \begin{tabular}{c}
          thick\\
          clients
        \end{tabular}
      }
    (y);
  
  \path[arrow]
    (c1) --
      node[plain, sloped, above]{faster computers}
    (c2);
  \path[arrow]
    (c3) --
      node[plain, sloped, above]{faster network}
    (c4);
\end{tikzpicture}