Consumer spending accounts for more than two-thirds of the economy, so if you know how the consumer sector is faring, you'll have a pretty good handle on where the economy is headed. Needless to say, that's a big advantage for investors.
The pattern in consumer spending is often the foremost influence on stock and bond markets. For stocks, strong economic growth translates to healthy corporate profits and higher stock prices. For bonds, the focus is whether economic growth becomes excessive and leads to inflation. Ideally, the economy walks that fine line between strong growth and excessive (inflationary) growth. Retail sales not only give you a sense of the big picture, but also the trends among different types of retailers. Perhaps auto sales are especially strong or apparel sales are showing exceptional weakness. These trends from the retail sales data can help you spot specific investment opportunities, without having to wait for a company's quarterly or annual report.
Balance was achieved through much of the nineties. For this reason alone, investors in the stock and bond markets enjoyed huge gains during the bull market of the 1990s. Retail sales growth did slow down in tandem with the equity market in 2000 and 2001, but then rebounded at a healthy pace between 2003 and 2005. By 2007, the credit crunch was well underway and starting to undermine growth in consumer spending. Later in 2008 and 2009, the rise in unemployment and loss of income during the recession also cut into retail sales. Spending rebounded in 2010 and 2011 but was constrained by lingering high unemployment.