  We believe the Babcock--Leighton process of poloidal field generation to be
the main source of irregularity in the solar cycle. The random nature of this
process may make the poloidal field in one hemisphere stronger than that in the
other hemisphere at the end of a cycle. We expect this to induce an asymmetry
in the next sunspot cycle. We look for evidence of this in the observational
data and then model it theoretically with our dynamo code. Since actual polar
field measurements exist only from 1970s, we use the polar faculae number data
recorded by Sheeley (1991) as a proxy of the polar field and estimate the
hemispheric asymmetry of the polar field in different solar minima during the
major part of the twentieth century. This asymmetry is found to have a
reasonable correlation with the asymmetry of the next cycle. We then run our
dynamo code by feeding information about this asymmetry at the successive
minima and compare with observational data. We find that the theoretically
computed asymmetries of different cycles compare favourably with the
observational data, the correlation coefficient being 0.73. Due to the coupling
between the two hemispheres, any hemispheric asymmetry tends to get attenuated
with time. The hemispheric asymmetry of a cycle either from observational data
or from theoretical calculation statistically tends to be less than the
asymmetry in the polar field (as inferred from the faculae data) in the
preceding minimum. This reduction factor turns out to be 0.38 and 0.60
respectively in observational data and theoretical simulation.
