Not just Kiambu,All over GEMA.
People just like animals give birth when they have sufficient to eat...majority Kikuyu don't have land, animals or grazing pastures while they no longer have monopoly in the government unlike in the past, that means they have to become slaves in mjengo,urban settlements,middle east slaves,maids and that means massive depopulation because you don't expect a maid in dubai,koinange street prostitute or mjengo woman to have more than two children.
To make the matters worse, you don't expect a so called university graduate corporate bitch or immigrant (who works long hours) to have kids.
All that leads to moral decadence, broken families, alcoholism, single parenthood and low birth rates.