News articles are written to SCARE!! We have to put that number in perspective.
in a city of 12,000,000, a 1% drop is not all that significant considering all the people moving in and out of the city each year. You do have go out of your way to register to vote. You can't register if you have a felony conviction on your record, EVER... So if any of those people got a felony conviction, well...
The largest majority of the numbers that the article is citing just failed to reregister and became "inactive". Some could have moved to another city/county and then voted there. Some may have died and new voters replaced them.
This article is VERY deceptive at best.