Question: For what gender is the quantity of bone marrow stem cells generally higher for the reproductive years?
About the article "Stem cell", section "Adult".

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Adult stem cells, also called somatic (from Greek Σωματικóς, "of the body") stem cells, are stem cells which maintain and repair the tissue in which they are found.
They can be found in children, as well as adults.
Pluripotent adult stem cells are rare and generally small in number, but they can be found in umbilical cord blood and other tissues.
Bone marrow is a rich source of adult stem cells, which have been used in treating several conditions including spinal cord injury, liver cirrhosis, chronic limb ischemia and endstage heart failure.
The quantity of bone marrow stem cells declines with age and is greater in males than females during reproductive years.
Much adult stem cell research to date has aimed to characterize their potency and self-renewal capabilities.
In mice, pluripotent stem cells are directly generated from adult fibroblast cultures.
However, mice do not live long with stem cell organs.
Most adult stem cells are lineage-restricted (multipotent) and are generally referred to by their tissue origin (mesenchymal stem cell, adipose-derived stem cell, endothelial stem cell, dental pulp stem cell, etc.
Adult stem cell treatments have been successfully used for many years to treat leukemia and related bone/blood cancers through bone marrow transplants.
Adult stem cells are also used in veterinary medicine to treat tendon and ligament injuries in horses.
The use of adult stem cells in research and therapy is not as controversial as the use of embryonic stem cells, because the production of adult stem cells does not require the destruction of an embryo.
Additionally, in instances where adult stem cells are obtained from the intended recipient (an autograft), the risk of rejection is essentially non-existent.
Consequently, more US government funding is being provided for adult stem cell research.
There are two points of view.
For the stem cells and other undifferentiated blood cells in the bone marrow, the determination is generally explained by the "determinism" theory of haematopoiesis, saying that colony stimulating factors and other factors of the haematopoietic microenvironment determine the cells to follow a certain path of cell differentiation.
This is the classical way of describing haematopoiesis.
The other point of view is "stochastic" theory: Undifferentiated blood cells are determined to specific cell types by randomness.
The haematopoietic microenvironment prevails upon some of the cells to survive and some, on the other hand, to perform apoptosis and die.
By regulating this balance between different cell types, the bone marrow can alter the quantity of different cells to ultimately be produced. 
For over 30 years, bone-marrow, and more recently, umbilical-cord blood stem cells, have been used to treat cancer patients with conditions such as leukaemia and lymphoma.
During chemotherapy, most growing cells are killed by the cytotoxic agents.
These agents, however, cannot discriminate between the leukaemia or neoplastic cells, and the hematopoietic stem cells within the bone marrow.
It is this side effect of conventional chemotherapy strategies that the stem cell transplant attempts to reverse; a donor's healthy bone marrow reintroduces functional stem cells to replace the cells lost in the host's body during treatment. 
Bone marrow is the flexible tissue in the interior of bones.
In humans, red blood cells are produced by cores of bone marrow in the heads of long bones in a process known as hematopoiesis.
On average, bone marrow constitutes 4% of the total body mass of humans; in an adult weighing , bone marrow typically accounts for approximately .
The hematopoietic component of bone marrow produces approximately 500 billion blood cells per day, which use the bone marrow vasculature as a conduit to the body's systemic circulation.
Bone marrow is also a key component of the lymphatic system, producing the lymphocytes that support the body's immune system.
Bone marrow transplants can be conducted to treat severe diseases of the bone marrow, including certain forms of cancer.
Additionally, bone marrow stem cells have been successfully transformed into functional neural cells, and can also potentially be used to treat illnesses such as inflammatory bowel disease. 
The iliac crest has a large amount of red bone marrow, and thus it is the site of bone marrow harvests (from both sides) to collect the stem cells used in bone marrow transplantation.
The iliac crest is also considered the most ideal donor site for bone grafting when a large quantity of bone is needed.
For example, oral surgeons will often use iliac crest bone to fill in large osseous defects of the oral cavity caused from severe periodontal disease, excess bone resorption following tooth loss, trauma, or congenital defects including alveolar clefts.
The top of the iliac crests also marks the level of the fourth lumbar vertebral body (L4), above or below which lumbar puncture may be performed.