  The air-fluorescence yield is a key parameter for determining the energy
scale of ultra-high-energy cosmic rays detected by fluorescence telescopes. A
compilation of the available measurements of the absolute air-fluorescence
yield normalized to its value in photons per MeV for the 337 nm band at given
pressure and temperature has been recently presented in Ref. [1]. Also, in that
paper, some corrections in the evaluation of the energy deposited in the
corresponding experimental collision chambers have been proposed. In this note
this comparison is updated. In addition, a simple statistical analysis is
carried out showing that our corrections favor the compatibility among the
various experiments. As a result, an average value of 5.45 ph/MeV for the
fluorescence yield of the 337 nm band (20.1 ph/MeV for the spectral interval
300-420 nm) at 1013 hPa and 293 K with an uncertainty of 5% is found. This
result is fully compatible with that recently presented by the AIRFLY
collaboration (still preliminary) in such a way that including this latest
result could even lowered the final uncertainty below the 5% level with high
reliability.
