In what some experts are calling a strong indicator of improvement in the economy, Republicans in recent weeks have begun renewing their claims that President Barack Obama was not born in the United States. While most economists agree that any significant improvement in the U.S. economy is generally accompanied by an uptick in G.O.P. questions about Mr. Obamas place of birth, there is now an econometric tool for measuring the increase in those claims: the so-called S. & P. Birther Index. The Birther Index, established in 2008, measures the occurrences of such words as birth certificate, Kenya, and wasnt born here in Republican statements about the President, and has proven to be a surprisingly reliable tool for tracking improvements in the economy. Harland Dorinson, the economist who devised the S. & P. Birther Index, said that as the economy recovers the index also shows a strong surge in statements questioning the Presidents Christianity. As unemployment started going down, we saw an increase in references to Mr. Obama being a Muslim, he said. This is generally a very bullish sign for the economy. But Mr. Dorinson was quick to add that while the surge in references to Mr. Obama being an Islamic socialist born in a mud hut in Nairobi is encouraging, the economy is not out of the woods yet. We wont be fully in a recovery until the Republicans start calling him a Wiccan, he said. And if they start saying hes a Satanist who practices human sacrifice and drinks the blood of children, then itll be time to pop open the champagne. 