I don't know about total disposable income changes, but the net impact for low-wage workers will be bad. I don't know if you saw the recent study of Seattle, who raised their minimum wage to US$13? 
They found a total reduction of $100 million! for low-wage workers - working out to $125 per month, per job. (But note that the study is not yet peer reviewed). 


https://www.washingtonpost.com/news/wonk/wp/2017/06/26/new-study-casts-doubt-on-whether-a-15-minimum-wage-really-helps-workers/?utm_term=.e4fab07e0bde


https://evans.uw.edu/sites/default/files/two%20page%20overview.pdf