pgfplots ybar - how to adjust spacing between sets of data

Question

I would like to plot some data in a bar chat using ybar. The data corresponds to years on the x-axis. Now, for some years I have three data values to plot and for others only one value. The problem is when I use ybar, the space between the sets of data is not uniform. How can I make the spacing uniform such that the space between the data sets is uniform? Here's my MWE:

\documentclass{standalone}

\usepackage{pgfplots}

\begin{document}
        \begin{tikzpicture}
        \begin{axis}[
        %small,
        ybar,%=8pt, % configures ‘bar shift’
%       ybar interval=0.05,
        enlargelimits=0.25,
%       enlarge x limits={abs=1cm}, % The distance between the center of the first bar and the left edge
        ylabel={PMU Count},
        symbolic x coords={2009, 2013, 2014, 2015},
        xtick=\empty,
        %tick label style={font=\footnotesize},
        legend style={at={(0.5,-0.15)},
            anchor=north,legend columns=-1},
        nodes near coords,
        every node near coord/.append style={font=\tiny},
        nodes near coords align={vertical},
        ymode=log,
        point meta=rawy,
        extra x ticks={2009, 2013, 2014, 2015}, 
        extra x tick labels={\kern-12mm 2009,\kern-4mm 2013,\kern-12mm 2014,\kern8mm 2015},
        every x tick/.style={white},
%       x=2cm,% Distance between the centers of the bars
        ]
        \addplot coordinates {(2009, 200) (2014, 1700)};
        \addplot[fill=green]  coordinates {(2013, 60)};
        \addplot[fill=gray!50]  coordinates {(2015, 30)};
        \addplot[fill=red!80]  coordinates {(2015, 2400)};
    \legend{N,I,B,C}

        \end{axis}
        \end{tikzpicture}

\end{document}

Answer 1

This is not yet an answer. I simply didn't understand the question very well.

What's wrong with the figure produced by the following code?

\documentclass{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}

\begin{tikzpicture}
\begin{axis}[grid=major,xtick={2008,2009,...,2016},
    x tick label style={rotate=90,
        /pgf/number format/1000 sep=},
    ylabel=Population,
    enlargelimits=0.15,
    legend style={at={(0.5,1.15)},
        anchor=north,legend columns=-1},
    ybar,
    bar width=3pt,
]
\addplot
    coordinates {(2009,200) (2010,-100) (2011,-100) (2012,-100) (2013,-100) (2014,1700) (2015,-100)};
\addplot
    coordinates {(2009,-100) (2010,-100) (2011,-100) (2012,-100) (2013,60) (2014,-100) (2015,-100)};
\addplot
    coordinates {(2009,-100) (2010,-100) (2011,-100) (2012,-100) (2013,-100) (2014,-100) (2015,30)};
\addplot
    coordinates {(2009,-100) (2010,-100) (2011,-100) (2012,-100) (2013,-100) (2014,-100) (2015,2400)};

\legend{First,Second,Third,Fourth}
\end{axis}
\end{tikzpicture}


\end{document}

I used your data as well as other data with constant negative value in order to make you see that the bars are correctly centered with respect to sticks. The resulting figure is the following: