Because 2012 is the first election year following redistricting, the number of signatures needed for minor party and independent candidates for U.S. House in Illinois and Pennsylvania is significantly lower than in normal years.
In Illinois, in a normal year, the petition is 5% of the last vote cast. That means the typical U.S. House district following a presidential year needs, on the average, 14,000 signatures; and following a midterm year, 10,000. But Illinois law says in the year after redistricting, the requirement is exactly 5,000 signatures.
In Pennsylvania, in a normal year, the U.S. House petition is 2% of the winning candidate’s vote in the last election. But in years after redistricting, the new districts didn’t exist in the last election. So, instead, the state uses a different base for the percentage. Instead of 2% of the winner for Congress two years previously, it calculates what the winner of the preceding odd-year judicial election received in the new district. This is a lot of work for election officials. It also means that because the turnout is so much lower in the odd-year election years, the calculation produces a lower number. In 2012, in the average U.S. House district in Pennsylvania, an independent, or the nominee of an unqualified party, needs 1,144 signatures. By contrast, in 2010 the requirement in the average district was 3,842 signatures. Thanks to John Murphy for this news. UPDATE: it turns out that another clause in the Pennsylvania election law requires minor party and independent candidate requirements to never be less than what Democrats and Republicans need to get on the primary ballot. That number for major party members is 1,000 signatures to run for U.S. House, so this year minor party and independent candidates need between 1,000 and 1,961 signatures, depending on which district the candidate is running in.