The Himalaya by the Numbers: A Statistical Analysis - Himalayan ...

The results indicate that the spring season is more favorable in the central and far
eastern regions of Nepal, areas that are prone to heavy snowfall and avalanching,
while the autumn season is more favorable in the Khumbu-Makalu-Rolwaling and
in the western regions of Nepal. The Khumbu region is still slightly more favorable
in autumn when the expeditions to Ama Dablam, Cho Oyu, and Everest are factored
out (Ama Dablam and Cho Oyu are best in autumn while Everest is best in spring as
shown in Table A-8).
Table and Chart A-9b show member ascent counts and rates by season broken out by
geographic regions for the 6000m and 7000m peaks.
When only peaks under 8000m are considered, only the Annapurna-Damodar-Peri and
Langtang-Jugal regions remain significantly more favorable in the spring since the
Manaslu-Ganesh and Kangchenjunga-Janak regions are skewed by the higher spring
success rates on Manaslu and Kangchenjunga (see Charts A-8 and 9a). The Dhaulagiri-
Mukut region becomes significantly more favorable in the autumn when the high
spring success rate on Dhaulagiri I is factored out. The Khumbu-Makalu-Rolwaling
region is neutral when Ama Dablam is omitted.
Ascents by Expedition Years
Chart A-10 shows member ascent rates by expedition years in 5-year steps for all
peaks.
The results from the early years from 1950 to 1970 are more erratic due to the lower
numbers of expeditions, especially in the late 1960s when Himalayan climbing was
suspended in Nepal and before the Chinese side of the border was opened to foreign
climbers in 1980. From the 1970s onward, the data in Chart A-10 show more consistent
results as the trend lines show a steady increase in member ascents and ascent rates
for all peaks combined.
Chart A-11 shows member ascent rates over time broken out by altitude. The rates for
the 6000ers and 7000ers are relatively even, 40-50% for the 6000ers and 20-25% for the
7000ers. Only for the 8000ers has there been a steady increase since 1970, starting at
about 7% in 1970 and increasing to 40% after 2000.
Charts A-12 through A-14 give a more detailed view of member ascent rates since 1970
when segregating out the ACE commercial routes. These commercial peaks show a
more rapid increase in ascent rates during the last 15 years. For the 6000ers, there
actually has been a decrease in ascent rates when Ama Dablam is removed, possibly
due to recent emphasis on exploratory expeditions to the newly opened 6000m peaks.
For the 8000ers, there has been an increase in ascent rates for peaks other than Cho
Oyu and Everest, most likely due to the increasing interest in climbing all of the
fourteen 8000ers.
Chart A-15 shows member ascent rates for only the commercial routes on Ama
Dablam, Cho Oyu, and Everest since 1990.
Charts A-16 through A-18 compare member ascent rates on Ama Dablam, Cho Oyu,
and Everest for the commercial routes and the non-commercial routes since 1970. Only
Everest shows an increase in member ascent rates for the non-commercial routes.
50 Ascent Analysis