There are a number of things that can contribute to the poverty rate. Illegals entering this country, for instance, can play a role. Where the surveys are sent plays a role. How many of the surveys get returned plays a role. The state you live in plays a role. CA for example has the 2nd highest poverty rate in the country. But overall, the poverty rate really isn’t changing that much in the country as a whole. This link:
https://poverty.ucdavis.edu/faq/what-current-poverty-rate-united-states
Shows the historical trend in poverty from 1959 through 2015, but the article also states the 2016 poverty which is right in line with the rest. Since the poverty is only calculated every year, this is about as accurate as you can get.