An examination of the percentage of the total Soottish poll gained by the SNP at general elections between 1951 and 1974 inclusive suggested that a stable, sigmoidal growth process might be identified if elections were regarded as occurring at unit intervals in time. The resulting time service was extremely well-fitted by Pearl's Law, a theoretical growth curve possessing a signoidal trend, and a theoretical upper limit to growth. On the basis of this model, estimated of, and confidence intervals for, both this theoretical upper limit, and of the party's performance in the next general election were obtained.