Adjusted for a weaker U.S. dollar, S&P 500 gains in 2017 were less impressive than meets the eye, and offer yet another reminder why portfolios should diversified globally, according to analysts at New Frontier Advisors. The S&P 500 SPX, -0.06% rose 19.4% last year, fueled by optimism over corporate tax cuts and favorable economic growth environment as well as low inflation. The stock market performance, attributed in part to a strengthening economy, stands in contrast to a flattening yield curve and a weakening U.S. dollar, both of which signal low economic growth in the long term. The yield curve—the difference between short-dated and long-dated yields—has been flattening steadily since 2013, when it was at about 265 basis points. The spread between two- TMUBMUSD02Y, +0.20% and 10-year Treasury yields TMUBMUSD10Y, -0.21% is currently at 60 basis points. An inverted yield curve preceded all of the past seven recessions, but a flattening yield curve does not always mean it will invert. In fact, the yield curve steepened over the past few weeks after narrowing to 48 basis points.via