Complex sentence: For years, NAIA has collected data from shelters across the country to document the status of pet and companion animal populations, as the Humane Society and PETA raise funds and have argued for certain legislation based on an alleged problem of "pet overpopulation".
Split into simpler sentences: For years, NAIA has collected data from shelters across the country to document the status of pet and companion animal populations. The Humane Society and PETA have raise funds and argued for certain legislation based on an alleged problem of "pet overpopulation".