The last time the U.S. economy was posting surprising economic growth numbers amid rapid wage gains and moderating inflation, Ace of Base and All-4-One topped the Billboard charts and denim overalls were in vogue. Thirty years ago, officials at the Federal Reserve were hotly debating whether the economy could continue to chug along so vigorously without spurring a pickup in inflation. And back in 1994, it turned out that it could, thanks to one key ingredient: productivity. Now, official product