Common numbers / statistics for Uniquely mapped reads?

Was asked if there was a commonly reported numbers for
uniquely mapped reads (which is troublesome to define with bowtie)
vs
total mapped reads

Not sure also if the numbers differ for applications
e.g.
WGS
exome reseq

human vs other organisms.
Got this figure from a 2009 paper. Not sure if anyone collates data like this
http://bioinformatics.oxfordjournals.org/content/25/7/969.full.pdf