biblatex: parentheses around the volume number of an article

Question

What do I have to write in the preamble to bring the bibliography to make parentheses around the volume number of an article? I'm using the authoryear style.

Here is an example:

\begin{filecontents}{filename.bib}
@article{Billio.2012,
author = {Billio, Monica and Getmansky, Mila and Lo, Andrew W. and Pelizzon, Loriana},
year = {2012},
title = {Econometric measures of connectedness and systemic risk in the finance and insurance sectors},
pages = {535--559},
volume = {104},
number = {3},
journal = {Journal of Financial Economics}
}
\end{filecontents} 
\documentclass{article}
\usepackage[hyperref=true,
            maxcitenames=4,
            isbn=false,
            dashed=false,
            style=authoryear,
            backend=bibtex,
            firstinits=true]{biblatex}
\bibliography{filename.bib}
\begin{document}
\cite{Billio.2012}
\newpage
\renewcommand\refname{List of Literature}
\printbibliography[heading=bibintoc]
\end{document}

Any help is appreciated.

Answer 1

Change the number field format for @article (already hinted by Jörg) and redefine the volume+number+eid bibmacro to remove the dot after the volume (and add a non-breaking space or thin space if desired).

\documentclass{article}

\usepackage[style=authoryear,firstinits=true]{biblatex}

\renewbibmacro*{volume+number+eid}{%
  \printfield{volume}%
%  \setunit*{\adddot}% DELETED
  \setunit*{\addnbspace}% NEW (optional); there's also \addnbthinspace
  \printfield{number}%
  \setunit{\addcomma\space}%
  \printfield{eid}}
\DeclareFieldFormat[article]{number}{\mkbibparens{#1}}

\usepackage{filecontents}

\begin{filecontents}{\jobname.bib}
@article{Billio.2012,
author = {Billio, Monica and Getmansky, Mila and Lo, Andrew W. and Pelizzon, Loriana},
year = {2012},
title = {Econometric measures of connectedness and systemic risk in the finance and insurance sectors},
pages = {535--559},
volume = {104},
number = {3},
journal = {Journal of Financial Economics}
}
\end{filecontents} 

\addbibresource{\jobname.bib}

\nocite{*}

\begin{document}

\printbibliography

\end{document}

More information at Guidelines for customizing biblatex styles.