From the journals of the Entomological Society of America, we note a study out of Department of Environmental Biology, Guelph University, Canada, on the Influence of Pollen Diet in Spring on Development of Honey Bee (Hymenoptera: Apidae) Colonies:
A 3-year study on pollen and pollen-substitute feeding in spring suggests that there was little difference in effect between the two diets. Feeding the bees a pollen or a pollen-substitute, either one, helped the colonies to build up in the spring — however —
an investment in supplementing the pollen diet of colonies would be returned for situations in which large spring populations are important, but long-term improvement in honey yields may only result when spring foraging is severely reduced by inclement weather.
So, if I’m reading this right, the decision of whether a beekeeper will get a good return on money invested in spring pollen supplements for the bees is going to depend on the likelihood of poor foraging weather, and how stressed the bees are likely to be (larger spring populations might be more important for commercial honey producers and pollination services). So, with a good long-term weather forecast, lots of nectar-and pollen-bearing plants within easy forage range of the apiary, and a hobby bee operation where the colonies are not transported or put to monoculture crops, there might be no great benefit in giving extra pollen. Something to keep in mind when planning your spring beekeeping.
The full report has a cost attached, but you can read the short Abstract online, free of charge.