Property assessment has long been a solid industry with steady work for those willing to undertake the education and training required to enter the field. But that stability is changing thanks to automation. The number of appraisers is shrinking as software gets more accurate at valuing property and is increasingly integrated into the sale process. Benjamin Keys, Wharton professor of real estate, and Stan Humphries, chief analytics officer at online real estate marketplace Zillow.com, recently appeared on the Knowledge at Wharton show on SiriusXM channel 111 to discuss the changes and where the industry is headed. (Listen to the podcast at the top of this page.) Following are key takeaways from their conversation: The margin of error is decreasing as automation improves. Zillow offers a tool it calls Zestimate that uses input factors to determine the worth of a property. The Zestimate, which has been around since the website’s inception in 2006, cannot be considered an official, certified appraisal.…