This December, the usual bull-versus-bear debate will take place on the direction of the industrial economy as it enters 2020. While no definitive answers will come this month, truck manufacturer Navistar International (NYSE: NAV), industrial supply company Fastenal (NASDAQ: FAST), and delivery giant FedEx (NYSE: FDX) will release data that will say a lot about prospects for investing in 2020. Here's what to look out for. Image source: Getty Images. Navistar: Trucking as a hot sector? According to most industry forecasts and current trends, the trucking sector is set for a severe contraction in 2020, as it normalizes from a couple of years of torrid growth that followed the slowdown in heavy industries caused by the slump in commodity prices in 2015-2016: US Heavy Truck Sales data by YCharts. However, it looks like this news has largely been priced into top stock valuations. The really important questions are: When will heavy-duty truck sales start to bottom, and will that be in 2020? They're questions that investors will be looking for clues on when Navistar presents fourth-quarter earnings in late December. As you can see from Navistar's forecasts, industry production is set to decline in 2020: Data source: Navistar presentations. Includes bus, medium- and heavy-duty trucks, and severe-service trucks. However, as we saw with the remarkable turnaround in trucking stocks in 2016, investors are likely to anticipate the pickup in truck sales and buy in ahead of it. Note how stock prices rose even as truck sales fell in 2016: NAV data by YCharts. The chart below shows the consensus forecasts for earnings for 2019 and 2020. Valuations look attractive -- provided they mark a cyclical low point, and truck sales and production stabilize and start to grow in 2021. Investors will be eagerly listening to what Navistar says on the matter during the earnings call because the trucking sector could be an attractive area to invest in 2020: Company 2019 EPS Estimate 2020 EPS Estimate P/E Ratio 2019 P/E Ratio 2020 Navistar $2.32 $2.76 14.1 11.8 PACCAR $6.86 $5.47 11.9 14.9 Meritor $3.82 $2.82 6.6 9.0 Cummins $14.89 $12.92 12.3 14.2 Dana $3.04 $3.06 5.6 5.5 Data source: Yahoo Finance. Fastenal: Manufacturing and construction Industrial supply companies give great color on the economy -- always have and always will. The reason is that their sales cycles tend to be very short, and when a slowdown (or an acceleration) occurs in the industrial economy, you'll see it first in their sales figures. Fortunately, Fastenal publishes its sales information every month, something investors should look out for. Unfortunately, the data for October showed an ongoing slowdown in manufacturing. But investors will be hoping that construction data builds on signs of stabilization from September and October: Data source: Fastenal investor presentations. Perhaps the best way to look at matters is to focus on sequential growth trends compared to historical benchmarks given by Fastenal in earnings presentations; this gives a better measure of when conditions might stabilize. October certainly wasn't a good month from this perspective, so investors will be hoping the November data is significantly better than the historical benchmark of a 4% decline in sales from October to November -- something to look out for if you want to invest in the manufacturing sector in 2020. Data source: Fastenal investor presentations. FedEx: The global economy and peak delivery season It's not been an easy year for investors in FedEx. While its rival UPS (NYSE: UPS) has largely kept pace with the S&P 500, with a nice rise of 23%, FedEx's stock has slightly declined in 2019. It's certainly true that a combination of the trade war and the slowdown in the industrial sector has negatively impacted FedEx's revenue and earnings expectations, but that doesn't explain the relative outperformance of UPS. In fact, in its most recent quarter, UPS managed to increase margin across all of its segments. And it demonstrated that it's getting a grip on reducing the cost of e-commerce deliveries and moderating its elevated level of capital spending; UPS has ramped up spending in order to service future e-commerce delivery growth. In other words, UPS is demonstrating that it's on track to marry e-commerce growth with margin and earnings growth, as well as free cash flow expansion. FedEx, in contrast, opened its fiscal 2020 by lowering its full-year 2020 earnings guidance, and guiding toward another year of heavy capital expenditures in 2021: Data source: FedEx investor presentations. Meanwhile, the integration of its TNT acquisition is running behind management's initial expectations. Investors will be hoping FedEx steadies the ship by not cutting guidance again, while outlining how its trading is faring in the all-important holiday season -- peak delivery days always strain the networks of package-delivery companies. If FedEx can do this when it gives results before Christmas, investors might warm to its prospects in 2020. Three things to look out for Industrial-sector watchers and investors will be hoping for signs of stabilization in Fastenal's sales data for November. They'll also watch for FedEx's commentary on the economy, and how it's dealing with margin challenges due to burgeoning e-commerce deliveries. Meanwhile, if trucking is going to be a great investment idea for 2020, then Navistar's management should be talking about signs of bottoming in the near future. 10 stocks we like better than FedExWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has quadrupled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and FedEx wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of June 1, 2019 Lee Samaha has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends FedEx. The Motley Fool owns shares of Paccar. The Motley Fool recommends Cummins and Fastenal. The Motley Fool has a disclosure policy.Source