size (see Sect.\[sect:simu\]). The tension with the results based on UV-detected galaxies could be explained by a slight incompleteness of the UV-detected samples at low sSFR or a small overestimate of the dust corrections. There could also be effects caused by the different techniques and assumptions used to determine the stellar masses in the various fields (star formation histories, PSF-homogenized photometry or not, presence of nebular emission in the highest redshift bins, template libraries, etc.). Finally, this difference could also be an effect of the variance. These discrepancies on the estimates of sSFRs will be discussed in detail in @Schreiber2014.\
\[fig:sSFR\]

![\[fig:ssfr\] Evolution of the mean sSFR in main-sequence galaxies (blue triangles) and strong starbursts (red squares). The gray diamonds are a compilation of measurements at the same mass performed by @Sargent2014. The blue line is the best fit to our data.](sSFR_z.eps)

Evolution of the mean intensity of the radiation field {#sect:U}
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![\[fig:U\] Evolution of the mean intensity of the radiation field $\langle U \rangle$ in main-sequence galaxies (blue triangles) and strong starbursts (red squares). The black diamonds are the measurements presented in @Magdis2012b based on a similar analysis but in the GOODS fields. The orange asterisk is the 