Harvesting recommendations are also based on other prognostic factors, among them estimates of reindeer population density, total population in various regions, and availability of adequate food sources. Since these estimates are difficult to make and can vary over time for each region, the recommendations and quotas are constantly adapted to the local needs, sometimes quite radically. Historically, Greenland's reindeer population has fluctuated widely. For example, it numbered around 100,000 in the early 1970s and then was believed to have dropped to about 9,000 in 1993. Hunting regulations reflected these mistaken and hotly debated estimates and harvesting was suspended from the summer of 1993 until the autumn of 1995, whereupon hunting was once again allowed.