MLPA offers exposure to US-listed midstream MLPs exclusively. Holding approximately 20-30 constituents, the fund narrows in on entities that focus on transportation, storage and processing of various energy products. Selected securities are weighted by market-cap, subject to capping constraints. Structured as a C-corporation, the fund pays taxes at the fund level, with the upside that its distributions are generally tax-deferred. The index rebalances quarterly. Prior to March 30, 2015, the fund tracked the Solactive MLP Composite Index which included exploration and production (upstream) and refining and marketing (downstream) firms.