Measurements are reported of the ferroelectric polarizationPsinduced in a non-chiral smectic C phase by a variety of chiral dopants having different molecular structural features. Using molecular calculations of contributing dipole moments, ferroelectric order parameters are determined from the experimental results. The relationships between thePsand various other molecular properties are discussed, and it is shown that restricted rotation of the molecule due to its shape and internal energy barriers to rotation can result in relatively high values ofPs. In contrast dipolar groups flexibly attached to a chiral centre may have their contribution toPsgreatly reduced through internal rotation.