NY Death Index Yonkers

I attempted to search the NYS Death Index from 1920-1925, for the death of Joseph Christie, of Yonkers NY through Ancestry. He was listed in the 1920 census as being less than one and was no longer with the family in the 1925 State Census. From the info regarding the collection, Deaths after 1914, where then transferred to the state, unless I read it incorrectly. Any suggestions? Thank you in advance. I will be back in NY in September the Yonkers Clerk's office can be a service hit or miss depending on who waits on you.