With stocks surging one moment and plunging the next, it's good to remember that, from 1926 through 2016, a portfolio diversified across stocks, bonds and cash averaged a 9.6% annual return, with a better risk-reward ratio than any one of the four investments with large liquid markets.

Ninety-one years goes back to when stock returns were first recorded on Wall Street, but most people don't invest for 91 years. The bar chart shows returns of the four investments versus the diversified four-asset portfolio over more realistic holding periods.

Over 35 years, large-company stocks beat their long-term average return over 91 years in a whopping 88% of the 35-year rolling periods! In contrast, over all of the 10-year rolling periods between 1926 and 2017, large-company stocks beat their 91-year return in only 46% of the 12-month rolling period.

In addition, the longer you stayed in the diversified portfolio, the more likely you were to experience the 91-year results. While holding the diversified portfolio for five years beat the 91-year return of 9.6% in 56% of the 12-month rolling periods over the 91 years, holding the four-asset portfolio for 35 years beat the 91-year results in 88% of the 12-month rolling periods. Diversification neither assures a profit nor guarantees against loss in a declining market and past performance is not a guarantee of future results, but these results show that the longer you invest, the more likely you are to experience the 91-year return and risk statistics.

Recently, volatility surged after investors were spooked by rising inflation and lending rates, and growing concern over the long-term U.S. debt. Statistically, the chance of a bear market decline of 20% or more increases as the nine-year bull market grows older, and the new tax law increased the chance of a Federal Reserve interest-rate policy mistake quashing growth for allowing inflation to surge. Fed mistakes caused every recession in post-World War II history.

However, earnings drive stocks and earnings expectations have recently surged. When the tax law was signed on December 22, 2017, the average company in the S&P 500 was expected to earn $131 a share in 2018, but that was revised to $152 and could be boosted again. S&P 500 operating earnings per share as of February 7, 2017 were $132.40 for 2017, $155.26 in 2018, and $170.93 in 2019, according to data from Yardeni Research, Inc. and Thomson Reuters I/B/E/S. According to independent economist Fritz Meyer, 2018 and 2019 estimates were revised up in December 2017 from, respectively, $146.19 and $160.69.

With real wages continuing to grow, consumers are spending and consumers account for 69% of economic growth. So, despite the recent correction, the bull market and economic expansion could strengthen and last many months longer.

US Large Cap represented by S&P 500 Total Return Index; US Small Cap represented by S&P Small Cap600 Total Return Index; US Bonds represented by Barclays US Aggregate Bond Index TR USD; Cash represented by USTREAS Stat UST-Bill 90 Day TR.