I disagree. "Slowed decline by 30%" to me means an absolute reduction of 30% in some rate expressed as unit X over unit time, and that's what I thought you mean

I disagree. "Slowed decline by 30%" to me means an absolute reduction of 30% in some rate expressed as unit X over unit time, and that's what I thought you meant until another commenter pointed out that it was a relative reduction. IMHO it's not an explicit callout unless you are using the words 'relative' and or 'absolute'