  We study the long-term behaviour of sunspot penumbra to umbra area ratio by
analyzing the recently digitized Kodaikanal white-light data (1923-2011). We
implement an automatic umbra extraction method and compute the ratio over eight
solar cycles (Cycles 16-23). Although the average ratio doesn't show any
variation with spot latitudes, cycle phases and strengths, it increases from
5.5 to 6 as the sunspot size increases from 100 $\mu$hem to 2000 $\mu$hem.
Interestingly, our analysis also reveals that this ratio for smaller sunspots
(area $<$ 100 $\mu$hem) does not have any long-term systematic trend which was
earlier reported from the Royal Observatory, Greenwich (RGO) photographic
results. To verify the same, we apply our automated extraction technique on
Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI)
continuum images (1996-2010). Results from this data not only confirm our
previous findings, but also show the robustness of our analysis method.
