Productivity must improve if the U.S. recovery and the six-year bull market is going to continue, Wells Capital Management's Jim Paulsen said Friday.

"Most post-war bull markets have been associated with better-than-average productivity growth. This has not been one of those," Wells' chief investment strategist said on CNBC's "Squawk Box." "If we don't get that, then I'm a little concerned about the longevity of the recovery."