This gives the graph I planned to have. The code is based on the (original) answer of @Zarko:
\begin{frame}
\frametitle{The Economy - Environment}
\center
\begin{tikzpicture}[>={Bar[width=4mm]},
tbox/.style ={font=\Large\bfseries\sffamily},
bbox/.style ={text width=4cm, align=left, inner sep=2mm}
]
\draw[very thick,<->] (-5,0) -- (5,0);
\draw[very thick,densely dashed] (0,2mm) -- (0,-2mm);
%
\node [tbox,above] at (-2.4,0) {DAY (DM)};
\node [tbox,above] at ( 2.4,0) {NIGHT (CM)};
%
\node [bbox,below right] at (-5,0) {xx xx xx xxx xxx xxx xxx\\
yy yy yyy yyy yyyy\\
zzzzz zz zzzz z z zzz};
\node [bbox,below right] at (0,0) {xx xx xx xxx xxx xxx xxx\\
yy yy yyy yyy yyyy\\
zzzzz zz zzzz z z zzz};
\tikzset{>=stealth}
\draw [very thick, <-] (-5.5,0mm) -- (-5.5, -10mm);
\draw [very thick, <-] (-6.2,0mm) -- (-6.2, 10mm);
\node [bbox,below right] at (-5.8,-1) {$\eta$};
\node [bbox,above right] at (-6.5,1) {$\mu$};
\end{tikzpicture}
\end{frame}

Tikz– May 20 '17 at 16:38