On the chart shown here, a huge percentage of professional services are directly related to the profit potential of oil and gas exploration and development. They are companies like Oceaneering and Halliburton. Those companies suffered in oil boon times.
I’m one of those.
While some are focused on oil production, many like me, provide services to them and others. Fluor, KBR, etc will provide services to oil/gas producers, movers and users. When upstream gets slow, downstream tend to get busier.