  We use a modified pulsar current analysis to study magnetic field decay in
radio pulsars. In our approach we analyse the flow, not along the spin period
axis as has been performed in previous studies, but study the flow along the
direction of growing characteristic age, $\tau=P/(2\dot P)$. We perform
extensive tests of the method and find that in most of the cases it is able to
uncover non-negligible magnetic field decay (more than a few tens of per cent
during the studied range of ages) in normal radio pulsars for realistic initial
properties of neutron stars. However, precise determination of the magnetic
field decay timescale is not possible at present. The estimated timescale may
differ by a factor of few for different sets of initial distributions of
neutron star parameters. In addition, some combinations of initial
distributions and/or selection effects can also mimic enhanced field decay. We
apply our method to the observed sample of radio pulsars at distances $<10$ kpc
in the range of characteristic ages $8 \times 10^4 < \tau < 10^6$ years where,
according to our study, selection effects are minimized. By analysing pulsars
in the Parkes Multibeam and Swinburne surveys we find that, in this range, the
field decays roughly by a factor of two. With an exponential fit this
corresponds to the decay time scale $\sim 4 \times 10^5$ yrs. With larger
statistics and better knowledge of the initial distribution of spin periods and
magnetic field strength, this method can be a powerful tool to probe magnetic
field decay in neutron stars.
