In those countries where dialect study is undertaken, dialectologists observe that there are today many factors militating against the strict maintenance of older dialect  the standardization of terminology as adopted by national periodicals, news services, radio, and television; the establishment of  prestige  dialects and, through the media, their promulgation; and the huge population shifts that have taken place, particularly in the U.S. since WWII.
( ( In ( ( those countries ) ( where ( ( dialect study ) ( is undertaken ) ) ) ) ) ( , ( dialectologists ( ( observe ( that ( there ( ( are today ) ( ( ( ( ( ( ( many factors ) ( ( ( militating ( against ( ( the ( strict maintenance ) ) ( of ( older dialect ) ) ) ) ) ( ( the standardization ) ( of ( terminology ( as adopted ) ) ) ) ) ( by ( ( ( ( ( ( ( ( national periodicals ) , ) ( news services ) ) , ) radio ) , ) and ) television ) ) ) ) ; ) ( ( the establishment ) ( of ( ( ( ( prestige dialects ) and ) ( , ( ( through ( the media ) ) , ) ) ) ( their promulgation ) ) ) ) ) ; ) and ) ( ( the ( huge ( population shifts ) ) ) ( that ( have ( ( ( ( taken place ) , ) particularly ) ( in ( ( the U.S. ) ( since WWII ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NP (DT those) (NNS countries)) (SBAR (WHADVP (WRB where)) (S (NP (NN dialect) (NN study)) (VP (VBZ is) (VP (VBN undertaken))))))) (, ,) (NP (NNS dialectologists)) (VP (VBP observe) (SBAR (IN that) (S (NP (EX there)) (VP (VBP are) (ADVP (NN today)) (NP (NP (NP (JJ many) (NNS factors)) (VP (VBG militating) (PP (IN against) (NP (NP (DT the) (JJ strict) (NN maintenance)) (PP (IN of) (NP (JJR older) (NN dialect))))) (NP (NP (DT the) (NN standardization)) (PP (IN of) (NP (NP (NN terminology)) (ADJP (RB as) (VBN adopted))))) (PP (IN by) (NP (NP (JJ national) (NNS periodicals)) (, ,) (NP (NN news) (NNS services)) (, ,) (NP (NN radio)) (, ,) (CC and) (NP (NN television)))))) (: ;) (NP (NP (DT the) (NN establishment)) (PP (IN of) (NP (NP (NN prestige) (NNS dialects)) (CC and) (PRN (, ,) (PP (IN through) (NP (DT the) (NNS media))) (, ,)) (NP (PRP$ their) (NN promulgation))))) (: ;) (CC and) (NP (NP (DT the) (JJ huge) (NN population) (NNS shifts)) (SBAR (WHNP (WDT that)) (S (VP (VBP have) (VP (VBN taken) (NP (NN place)) (, ,) (ADVP (RB particularly)) (PP (IN in) (NP (NP (DT the) (NNP U.S.)) (PP (IN since) (NP (NNP WWII))))))))))))))) (. .)))
The media and population shifts has contributed to variations on the older dialects.
( ( The ( media ( and ( population shifts ) ) ) ) ( ( has ( contributed ( to ( variations ( on ( the ( older dialects ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS media) (CC and) (NN population) (NNS shifts)) (VP (VBZ has) (VP (VBN contributed) (PP (TO to) (NP (NP (NNS variations)) (PP (IN on) (NP (DT the) (JJR older) (NNS dialects))))))) (. .)))