Perhaps you should try some spelling variations:
"per decrease" » "per decreased" (Expand Search), "per increase" (Expand Search)
"semi decrease" » "semi decreased" (Expand Search), "semi increase" (Expand Search), "sem decrease" (Expand Search), "sami decrease" (Expand Search)
"spent decrease" » "spent decreased" (Expand Search), "spent 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: "((((\"per decrease\") OR (((\"semi decrease\") OR (\"spent decrease\"))))) OR (\"mean decrease\"))~".
• Removing quotes may allow a broader search: (((( per decrease ) OR ((( semi decrease ) OR ( spent decrease ))))) OR ( mean decrease ))~.
• Adding a wildcard symbol may retrieve word variants: (((("per decrease") OR ((("semi decrease") OR ("spent decrease"))))) OR ("mean decrease"))*.