Ignoring immigration and emigration, the population of Swiss citizens decreased by 2 while the foreign population increased by 2. There were 3 Swiss men and 4 Swiss women who immigrated back to Switzerland. At the same time, there were 5 non-Swiss men and 8 non-Swiss women who immigrated from another country to Switzerland. The total Swiss population change in 2008 (from all sources, including moves across municipal borders) was an increase of 39 and the non-Swiss population change was an increase of 2 people. This represents a population growth rate of 1.9%. The age distribution, , in Pfeffingen is; 123 children or 5.6% of the population are between 0 and 6 years old and 344 teenagers or 15.6% are between 7 and 19. Of the adult population, 202 people or 9.2% of the population are between 20 and 29 years old. 160 people or 7.3% are between 30 and 39, 439 people or 19.9% are between 40 and 49, and 518 people or 23.5% are between 50 and 64. The senior population distribution is 343 people or 15.6% of the population are between 65 and 79 years old and there are 72 people or 3.3% who are over 80.  , there were 763 people who were single and never married in the municipality. There were 1,131 married individuals, 53 widows or widowers and 80 individuals who are divorced.  , there were 775 private households in the municipality, and an average of 2.6 persons per household. There were 144 households that consist of only one person and 50 households with five or more people. Out of a total of 784 households that answered this question, 18.4% were households made up of just one person and 2 were adults who lived with their parents. Of the rest of the households, there are 289 married couples without children, 306 married couples with children There were 25 single parents with a child or children. There were 9 households that were made up unrelated people and 9 households that were made some sort of institution or another collective housing. The historical population is given in the following chart:  The castle ruins of Pfeffingen, Engenstein, Münchsberg and Schalberg are listed as a Swiss heritage site of national significance. In the 2007 federal election the most popular party was the SVP which received 29.51% of the vote. The next three most popular parties were the FDP (20.91%), the SP (18.93%) and the CVP (17.7%).