Perhaps you should try some spelling variations:
"helped decrease" » "helped decreased" (Expand Search), "helped increase" (Expand Search)
"greater decrease" » "greater decreased" (Expand Search), "greater increase" (Expand Search)
"peter decrease" » "peter decreased" (Expand Search), "peter increase" (Expand Search)
"mean decrease" » "mean decreased" (Expand Search), "mean increase" (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"helped decrease\") OR (((((\"greater decrease\") OR (\"peter decrease\"))) OR (\"mean decrease\"))))~".
• Removing quotes may allow a broader search: (( helped decrease ) OR ((((( greater decrease ) OR ( peter decrease ))) OR ( mean decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("helped decrease") OR ((((("greater decrease") OR ("peter decrease"))) OR ("mean decrease"))))*.